I've recently bought Let's Go Eevee, my first Pokemon game in the last decade, but I've run into a wall. I keep wiping halfway through the Elite Four and I'm not sure what to do.

This is my team of personal favorites I don't care about dumb competitive stuff. They're all about level 75 and I've fed them as many candies as I could get. I've got nothing but STAB moves on each Pokemon but I still can't get past the ice girl.

Should I just keep grinding? I really don't know what the game expects me to do if Mewtwo is locked until after the game :/