There's not really a good way to keep the old way stone evos worked without making them an absolute pain in the ass for competitive without completely rewriting how movesets work or locking the ability to get the stones to the post-game.Tbh replaying Platinum currently, the point about being able to get a full team of 6 before gym 1 these days as opposed to this only being possible towards the end of the game without grinding -really- sticks out, and I, kind of, enjoy it how it used to be in a weird way? The games repeatedly state that training a full team is very difficult back then and use this to explain why enemy trainers -don't- use more than 2~3 Pokemon until the endgame. That's just not the case anymore though and you'll find yourself going up against important trainers using half your party length well into the level 50s(Something which would be fine if the games used bring 6 pick 3 or 4 like online play does, but that's a different story.)
Pokemon like Gyarados or the Pseudos, things you have to actively put effort into raising due to how slow they gain exp for example, are now easy to just slot in the back of your party forever until they evolve(previously this would slow down your exp gain via switch training or the exp share).
Stone evolutions are similarly emphasized conceived to be a trade off; lose out on moves by evolving early for extra stats, or get moves and deal with a weaker Pokemon for longer. That factor just doesn't exist anymore, however. As of SWSH/SV, you can, basically the moment you get to Mesagoza, get a fully evolved Arcanine or Ludicolo with their entire movepool available to you without the cost of a single resource beyond the stone itself.
This among other things is why I feel that the games have actually gotten significantly worse as RPGs go over time despite arguably being just as easy as ever lol.
Literally all RPGs have Exp work via the modern Exp method Pokémon is using, even some really old ones from like the SNES era. Exp being reduced by the amount of party members you use was never a thing in any other RPG.




