>>34091661megas, alola forms and UBs are interesting ideas in concept but ultimately fall flat in execution because GF doesnt want to put the effort to expand upon or follow through on them.
Megas are particularly gimmicky but they were something new and interesting, but have essentially been only added into SM as an after thought.
Alola forms have a lot of potential but are limited to gen 1 Pokemon and some of them are lazy palette swaps.
And UBs seemed like an interesting new element to throw into the formula as they were introduced as something different from Pokemon, but it turns out they're essentially glorified legendaries.