I can attest to this. I’m not very far, but as of and after Misty, the game caught up to all the leveling I’d done by catching a ton of things in Viridian Forest; trying to control my capturing might even make me under leveled by the time I reach the later Gyms. I’m currently trying out a strategy of catching just one of each species, and if I need to train I hunt down larger Pokémon.
It’s honestly more difficult than I expected, though I expect that’s partially due to the fact that most of the discourse around the game made it out to be ridiculously easy and simplistic when it’s really more or less just Kanto again - not some baby version of it. The only thing preventing me from getting trashed is one of the special starter moves, which I can swap out at will since I’m running Eevee.
I’m also playing with a team of Eevee, Clefairy, Jigglypuff, Vulpix, and Alolan Vulpix, with no intention of evolving anything, so it might get really hard by the end. Suggestions for slot 6 are open!