Man it really feels like people misunderstand this game.

This is not a game you play for years to come or 8 hours a day. Its not meant that way which you can clearly see in the very limited gameplay loop.

This game is perfect if you play it here and there a bit. You need to stretch your 400h of playtime over a year or so (or more years even).

You basically did everything in a short time and now complain?

Thats a very weird thing to say but you simply played the game "wrong" by burning through everything. This is on you, not the game. You cant complain about something when your own expectations are wrong. If you are looking for a game you can sink tons of hours into, AC is not it. That just means you have to inform yourself better about the games you want to buy.