There are a couple of things that I think are really annoying in sun/moon:
1. The miltank near the day care lady, that you aleays accidently talk to, wasting time
2. Excessivly long Z-move cutscenes, time to wait a minute for your attack
3. Opponents in the elite four with sturdy, it makes grinding for XP a lot longer because it shows sturdy, the they use full restores on them
4. Excessive amount of dialogue/cutscenes/mohn is rude enough to make you take out then replace pokemon to ev train in the poke pelagon
5. Poke bank fee, who has parents who wont pay it?
6. Trade evolutions, who nobody to trade with except for the people who ruin your life?
7. Excessively long egg hatching animation, who hates the nickname part eating up your time?
8. Being unable to change nicknames from over the GTS
9. Having tp spend hours on the GTS because you caught the wrong nature on your legendary
10. The battle tree hax, why does scarf guillotine even exist?