For me, Pokemon's classic battle system addresses one of the big difficulties with RPG design: status effects and action denial.
Under normal circumstances, you can't really get players to use status for the basic stuff. They're slow compared to just attacking when the enemy can't put up a fight. One option would be to not have any basic stuff and make every fight a challenge that needs to be respected, but that's going to encounter other issues in the kind of game Pokemon is (it kind of needs random encounters in some form for the collection aspect, after all). This would be extra risky with Pokemon's limited moveslots, but it's mitigated by how the catching mechanics work: you want to keep around a way to incapacitate without KOing even for random encounters you've seen dozens of times before (what if it's a shiny?!). Sometimes I wonder if Quick Balls were a mistake because they break this incentive.
So then, if the status moves are being used less in regular fights (and there's still plenty of status moves that don't help capture), what about the boss fights? On one hand, they need to be effective here to reward the player for doing something different than the default option. On the other, plenty of status effects can completely remove the threat of a single target. For a lot of other RPGs, bosses will have immunity or at least heavy resistance to status to prevent the latter problem, running straight into the former. A trainer boss in Pokemon doesn't have this problem: status can absolutely cripple a mon, but losing one mon doesn't end the entire fight. The non-trainer bosses in the current games need clunkier workarounds (such as the Starmobiles having the above-mentioned status immunity).
While writing this, I did notice that both the "normal encounters too irrelevant for status" problem and the "bosses too vulnerable to status" problem are exacerbated by the games having potions. By having a drain on items (and thus indirectly money) as a part of combat, there's an extra incentive to do as little of it as possible (for a bigger example of this being an issue, compare any game with breakable weapons). Meanwhile, a slow victory from damage-over-time becomes certain when the player can access an arbitrarily high amount of healing. So a change I think would be beneficial over the baseline is to automatically heal to full between fights in exchange for no healing items usable in-battle. In other words, bring back the Battle Frontier.
On a separate note, I feel like the games should stay 6v6 singles even though VGC is 4v4 doubles. A team preview where you're choosing a subset of your 6 mons isn't meaningful when the enemy is a static NPC and you have access to your entire box. As for singles vs doubles specifically, I think that singles is more conducive to designing boss fights. The dominance of Protect on account of the higher lethality seems like it would feel frustrating to be on the other side of similar to when bosses use evasion (the AI can't have the metagame knowledge to lead to mindgames), and I honestly get some enjoyment out of figuring out switch lines during challenge runs, most of which would just fold to a double-target. Besides, I'm a Spikes lover, so the "some things only matter in doubles" argument isn't as impactful as it could be.
