It is interesting to note that sales sell otherwise.
Kids do fall for those smoke and mirrors and get interested in the fancy scenic mechanic enough to buy them / ask their parents to.
Do they keep playing the game after finishing the story? No, not really, but that doesn't matter, they bought the game already.
I’m genuinely curious what super mechanic they will come for next gen. They already did form change, moves, and the two combined together, so what’s next? Maybe they should go back to Mega Evolution. It’s just debuted in Go, and as well as being prominent in Masters. It would be a good time to bring it back to profit off the hype.
We’re talking about in-game though- Megas and Z-Moves break the in-game difficulty, given very few trainers use it themselves so you can kind of just stomp every encounter. Dynamax is handled much, much better in-game as it's only available when the opponent also uses it, making it both more balanced and feel more special when you can use it (compared to steamrolling with mega lucario or spamming Skystrike Hawlucha in every fight)
Megas, yes they definitely break the game, but I don’t think Z-Moves break the game, or at least not on same level as Megas. Because of Z-Moves are part of the trials of Alola, there more widely distributed. That means there are more people who use them, like Kahunas, Trial Captains, and even generic NPCs, so it’s more fair in that case. It’s also noting that while Megas last for the entire battle, Z-Moves are one turn only, meaning they are much easier to mess up and waste than Megas. The only broken thing about Z-Moves was that in USM, the Rotom Dex could grant you multiple ones, which Is undeniably broken.
On the top Exp. Share and difficulty, I like having the Exp. Share on and it reduces time in grinding. Lot of RPGs like Xenoblade Chronicles and DragonQuest have built in EXP Share and can prove to be difficult.
Pokémon‘s difficulty lies in the fact that Bosses are given significantly less options than the players, for example; in SwSh, every trainer that is not a gym trainer/significant NPC has 0 IVs meaning even if you have a ditto team you still have an advantage over the NPCs since it is highly unlikely to have a team of 0 IV Pokemon. Lot of the bosses don’t even have full movesets. Allister is a pretty notorious example: He uses Mimikyu, but his Mimikyu does not know a single Fairy type move, which prevents it from countering Dark types. It doesn’t even have 4 moves. Most other RPGs have bosses have an unfair advantage over players, but in Pokémon it is the reverse, which is the real problem, not the Exp. Share.