>>51139058Take this with a grain of salt as I'm autistic as fuck, but my go-to has been romhacks like Polished Crystal and Crystal Clear. I've replayed vanilla Crystal hundreds of times to completion and still get a lot of enjoyment out of it each time, but romhacks which expand on the base game in a way that still feels mostly faithful has been the way to go for me. Particularly if they have new areas which feel like they could easily have been in the original.
Don't shy away from using whatever Pokémon you want, you can always do another playthrough later on. When I first played Crystal Clear, I kept going between what water-type I wanted on my team (mostly between the Kingdra line and the Lanturn line) and even though one may be objectively better than the other, disregarding "what's the best" and just playing with whichever I liked more at the time was fun.
I avoided romhacks for years because my brain was like "but it's not a real Pokémon game" but now I just look at it as a fresh way to enjoy the older games.