I can’t help but feel like Koga’s gym is exactly what I didn’t hope would happen with Let’s Go - Needlessly padding out the game. At least, that’s what I believe is going on, with only pokemon caught counting (and not ones that are just “seen,” i.e. you encounter a guy’s Gastly but never catch it).
Other than that, it’s mostly what I expected, in the sense that about half or more of gyms are really hand-holdy in their requirements. Surge and Blaine don’t seem different from the original games as far as I can tell, but other than them, Erika (whose requirement might as well not even exist) and Koga (whose requirement is outright padding) don’t really give an innate advantage for “new” requirements. Everyone else pretty much forces you to have some kind of advantage though, as Giovanni doesn’t have a mega pokemon to counter your mega, Brock doesn’t have any way to deal with a grass or water type all that well (especially with those x4 weaknesses), and Jasmine’s requirement puts you at a level above her strongest pokemon. About the only new requirement that’s any good is Misty’s, and that’s because you’re still a couple levels under her Starmie - Making it function more as a recommended level you need to fulfill than anything.