I tried to fight as many Trainers as I could, and never run from wild battles, and I still managed to only keep pace with the opponent's levels throughout the game, so having the EXP Share permanently on didn't hinder the experience or anything. It just reduced the amount of boring grinding I would have had to do otherwise. I'd like to think I had a well-balanced team. The latter four gym leaders gave me some difficulty with their Gigantimax Pokemon (I only survived Allister because of the 3 turn clause), especially if they managed to knock out my Dynamax Pokemon in one hit before I even had a chance to make a move. Raihan gave me a lot of difficulty, but that had a lot to do with me not knowing it was going to be all double battles all the way through, assuming he would have all dragons, leading off with some wrong type choices because of it, and it being very late at night. All in all, it reminded me a lot of the Totem Pokemon battles; surprisingly hard for a Pokemon game if you don't happen to coincidentally have the perfect counter in your team (I annihilated Nessa's Drednaw with Dynamax Thwacky and Kabu's Centiskorch with Dynamax Carkol). The Battle Tower is it's usual unforgiving self.
I think another factor to consider is that it seemed like my Pokemon couldn't learn any TMs, especially not the good ones, even the TRs. My most powerful fire move was Incinerate, right up to the final boss fight. When your whole team's movesets are weaker than previous games, that's going to make the game seem harder than it really is. Luck will determine whether you get Flamethrower, Earthquake, Thunderbolt, Ice Beam, Psychic, Energy Ball, Shadow Ball, etc. early, if at all.