>>718227858
Personally, I feel that every pokemon should have evolutions up to around lvl 90.
Not necessarily an equal number of evolutions.
Or equally spaced evolutions.
But every pokemon should have 5-8 evolutions, that scales them to be generally viable in the late game.
This would also the process of training up Pokemon a little more exciting since all substantive progression doesn't come to a dead stop at lvl 50.

Besides that, I think adding more branches to pokemon evolutions lines would be good.
Specifically, branches that are dependent on the way in which the player trains and treats their pokemon - not lame/arbitrary shit like weather, time, or whether you fed it a funny rock.
Also, provide more learnt moves.
At minimum, enough to properly fill out the full span of lvl 1 to 100.
At maximum, enough so that most moves learned by each Pokemon are unique to that pokemon.

These are pretty brute force, patch improvements that I'm surprised Gamefreak hasn't implemented over its long existence.
Honestly, the Pokemon's mechanics are pretty archaic and it might be more worthwhile to redesign the battling, capturing, and raising systems from scratch.