Exeggcute is an excellent card. The ability to freely put a card from your discard pile into your hand as many times as you like with no drawbacks is a very powerful effect. A lot of decks love using Exeggcute to better manage what resources they discard off of Ultra Ball, Junk Arm, Computer Search, and Superior Energy Retrieval. Including a single copy of Exeggcute means that you effectively change these cards' "discard 2" cost down to a reasonable 1. Egg can also be useful outside of its interactions with Item cards. Empoleon can Diving Draw away an Egg every turn instead of cards it wants to hold on to. Weavile can recycle 4 Eggs for its Villify attack every turn for a guaranteed damage floor of 120. Yanmega Prime can use Egg as a way to increase its hand size if it comes up short of a free attack with Insight. But is the Egg all its cracked up to be? Out of every Pokémon in your deck, Egg is probably the one you want to set face down as your Active the least. Of course, bad starters exist in every format. It's just a part of the cruel variance that comes with playing this incredible game. But you should at least be aware of the advantage you give your opponent when you start with an Egg. Most importantly, never expect your opponent to send your Egg to the discard pile for you. If your opponent is avoiding an easy knockout, don't be afraid to attach & retreat. One other thing that's outside of your control is getting Laserbank donked. The only way you can prevent this is to ask yourself: "Do I need to play Egg???" The answer is not always yes! While Egg's use can be recommended in a chunk of the format's decks, it doesn't need to be thrown into everything as a 1-of staple. In decks that only utilize Egg for its synergy with Item cards, you have to consider how much Egg, as a card that takes up a deck slot, is going to be saving you throughout the game. If you're running the standard count of Items that looks similar to 4 Junk Arm, 1 Computer Search, and anywhere from 1-3 Ultra Ball, you probably don't actually need Egg. If you're playing a deck that doesn't mind thinning its hand for Beach, sending cards to the discard pile for Dark Patch, Dynamotor, or Thundurus-EX's Raiden Knuckle, you probably don't need Egg. A good example of a deck that really needs Egg is Magnezone Prime. Magnezone is tight on space to begin with, something you'd pick out 70 good cards for and end up having to play the best 60. It also runs all four of the "discard 2 cards from your hand" items at high counts. Comparatively, Magnezone and decks like it are going to be seeing a lot more value out of a single Egg vs. decks that only play it without giving its use some more consideration.
Jirachi-EX is a rare example of a Black & White era card that saw a good amount of play when it was legal in Standard, but doesn't (or shouldn't) see much play in modern Legacy lists as a staple to make decks run smoother. While on paper, Jirachi provides an appreciated extra layer of consistency, the cost of putting it into play almost always outweighs the benefit. To begin with, the range of possible Supporters Jirachi can search out is much narrower compared to the formats Tapu Lele-GX and Lumineon-V were legal in. There's not as much of a Legacy equivalent to grabbing low-count copies of specific tech or board disruption cards like Guzma, Boss's Orders, Acerola, Hex Maniac, or Delinquent on a pivotal turn. While Pokémon Collector is a comparable card to setup supporters that Tapu Lele would grab like Bridget and Elm's Lecture, Collector is not typically played in Legacy due to the availability of better and more consistent setup options. In almost all cases, you'd just be grabbing a draw supporter for turn, like Juniper, PONT, or an N. Other search and setup cards, like Random Receiver, Tropical Beach, and Smeargle provide more value throughout the course of the game and can be used to replace Jirachi. The most important catch to Jirachi is that it has 90 HP--the lowest out of every Pokémon-EX--which means omnipresent bench snipers like Kyurem or Landorus-EX can whittle it down very fast. It's also an easy Catcher target and a free two prizes for Genesect-EX, Raikou-EX, or anything playing Dusknoir. A general consistency card has failed when you can't afford to use it against all of the format's strongest decks. So why would someone run Jirachi considering all of its drawbacks? A few decks still have a valid reason for playing it. For example, Gothitelle needs to find Skyla or Twins to establish item lock as quickly as possible. Weavile Eggs is a deck that uses Jirachi to both maintain its extremely high speed with a relatively low Supporter count, a comparatively positive prize trade, and to feed into Weavile's Villify attack. Ultimately, if you're an experienced player and have a specific use for Jirachi in mind, go for it. Otherwise, general deck consistency can be improved in less risky ways.
A long, long time ago, protecting your bench from your opponent's attacks was a deckbuilding commitment. You had to include and set up at least one thin line of a tech Stage 1 Pokémon if you wanted your board to be safe from spread or snipe threats. These Bench threats came at a similar cost- they usually took equally as much (or more) time to get into play. But that's all in the past! With the introduction of Landorus-EX, Raikou-EX, and Kyurem, it's now easier than ever for your opponent to take knockouts on your low HP benched Pokémon! Introducing... Mr. Mime! Your easy, simple, single card answer to these evil, sickening strategies. To date, Mime is arguably the best option for bench protection we've ever seen throughout the history of the game. Aside from being a splashable Basic, it has the unique trait of protecting your benched Pokémon from your own attacks, which is slightly relevant with cards like Donphan Prime and Cacturne in format (though, if you're playing either, you probably want that damage on your bench for various reasons anyways). Mime should be included as a one-of in nearly every deck, with the rare few lists opting to play two if they consist of entirely low HP (90 or below, usually) Pokémon. What matchups are good to bench Mime in? When is an appropriate time to bench Mime? Should I always bench Mime against decks that can hit my bench? Is there ever a downside to benching Mime? All very good questions! Let's start with common matchups. TDK, Landogarb, Rayeels (for Raikou), Keldeo (for Blastoise), and Darkrai are the five most common decks you'll see that can threaten to hit the bench for relevant numbers. Genesect would normally be included among these, but Mime shouldn't always be benched against Genesect (more on that later). Less common threats include Tyranitar Prime, Yanmega Prime, Kyogre & Groudon LEGEND, and Plasma Seismitoad. In your most common matchups, Mime should usually hit the board as soon as you're able to. Landorus and Kyurem are often hitting your bench on their first turn going second
Tropical Beach is best described as a blessing and a curse when it comes to Legacy; it's a powerful universal draw card that enables so many slower decks to set up far more consistently than they otherwise would be able to, but it comes at the cost of being one of the most unaccessible cards throughout the history of the game. With powerful hand thinning cards like Ultra Ball, Computer Search, and Junk Arm in format, it's easy to get your hand to a low size during your turn for a larger draw off of Beach at the end of your turn. On top of that, you can convert a Skyla immediately into draw the turn that you play it, rather than grabbing a Supporter for your next turn. Many setup focused decks like Empoleon, Flygon, and Accelgor all appreciate 3 to 4 copies to retain a good amount of momentum and draw into the combination of pieces they need to set up their stage 2 Pokémon turn after turn. Even decks that would seem like they'd have less of a reason to play Beach, like Black Kyurem or Rayeels, sometimes include a couple copies to run a little smoother on the first few turns of the game. Beach's second use is as a counter stadium to Virbank City Gym, an omnipresent danger that can threaten to turn two-hit knockouts into an OHKO against many decks that utilize Beach. Bumping Virbank during your turn can determine whether or not you'll be knocked out by poison going into your opponent's next turn. Of course, we can't talk about Beach without discussing its absurdly high accessibility barrier. Players looking to buy a single English copy will not only have to spend at least a few hundred dollars, but also find someone willing to sell one. In the end, if you're building Legacy in paper, you're probably gonna have to compromise and use proxies or World Championship copies.