There’s lot of things that bother me, and they mostly have to do with functionality (I can live with poor graphics and poor animationsc etc, but I can’t get over missing basic functionalities), but if I had to pick a SINGLE one most bothering aspect, it would be the lack of a proper UI unit selection box where units are displayed individually. This hurts my micro the most and annoys the hell out of me, as it did during the beta. It just makes it a pain to play, I just couldnt enjoy myself because of this alone, nevermind when you add the rest of the problems. So this would be my number 1 concern about AoE4.
A close second and also very annoying would be lack of proper custom hotkeys, especially nonexistence of “go to buildings X” hotkeys and “select all barracks/archery ranges etc” hotkeys that we got accustomed to from all AoE games.
In 3rd place would probably be the nonexistence of patrol function.
Now to other important mentions in no particular order: game has poor visual clarity - hard to tell what unit is what - same with buildings; no exclusive control groups that overwrite the ctrl group before; no global queue display on UI; minimap is hard to read; the fact that queued units are displayed individually rather than grouped (so they’ve done it the wrong way around for both UI selection box where they should be displayed individually instead of grouped, as well as queued units where they should be displayed grouped instead of individually, like what the hell were they thinking); no higher ground damage bonus; nonexistance of a small list of players in a corner of the screen so I can tell who is who (like we had before with the scores list); when you click other players unit - it wont tell you who that unit belongs too - it will just say “villager - English” instead of “villager - English - TheViper”; no unit stances; weird 4 selection box building setup instead of Basic/Advanced or Eco/Military; upgrades icons and unit icons look the same and are hard to tell apart; cant see market prices without hover; input lag; objectives are always visible even when irrelevant and take up too much space; camera zoom is too low.
There’s way more, but didnt want to mention bugs like game ends when host leaves game in custom game, or inability to see map after a game, or many others, as this are for sure mistakes rather than design choices.