Agreed honestly. Won't be going back to the franchise until they return mega evolution and actually give all pokemon with no pre-evolution or evolution a pre evolution and evolution.
The ability to fast EV train (which you were able to do in Oras with having a pokemon with pokerus and having heard battles with pokemon that provide EVs in a particular stat) needs to return.
There needs to be sensible canonical ties to the anime for example: crystal Onix. Just introduce it but as a region varient.
Giant ancient Jigglypuff and Alakazam (or was it Gengar???) Anyway just introduce or reintroduce the idea of bigger pokemon (which was in U moon and U sun with pokemon called totems). This would also include that huge Dragonite that was shown in the anime.
Include more split evolutions. For example a female machoke and Machamp evolution. An evolution with a pokemon being able to actually wield honedge (hint hint regular farfetched)
Different variants of Aegislash (ancient rome looking sword and shield, gladiator sword and shield, samurai sword and shield, fencing sword with retractable shield).