>>48636631There's a difference between having the game be hard to beat vs having a game force you to think occasionally to get through mild but varied and fun challenges but overall be relaxingly simple to actually progress through.
Pokemon in the past consistently fit into that second category up until the end of Gen 5 and veered back into it in Gen 7, messing it up only in 6 (due to poor balancing of the EXP share and megas) and 8 (due to the game forcing EXP share at all times; however, the difficulty was probably a bit better balanced here than in gen 6 if you didn't mess around too much since a few of the trainers did have relatively competent teams).
Needing pokemon to be "hard" is at the extreme end of a simple request for the game to give more interesting "dangerous" situations to puzzle out in creative ways.
As, at the core of things, people don't want a game to just do nothing but lie down and die for them if they use all the toys the sandbox gives them to play with. It's not really a matter of making it really hard or anything antithetical to pokemon's base pick up and play design. They want to play around with things and have the game give them a semblance of opposition so that it feels exciting to test things out and triumph by what feels like their own wit and creative application.
After all, even when you're actually 6 and not into all the extra competitive shit, it feels kinda hollow to have a Mewtwo but have nothing worthy of fighting with it after a little while.