Every rush strategy is already highly punished in Aoe4 as it has lots of defensive buildings that do shoot arrows with a hit rate of 100 %. Also, villagers can be garrisoned in lots of buildings. So this game is very supportive to a defensive beginner playstyle already. Punishing rush strategies even more will make this game a total turtle and boom fest with no interactions until castle age. That’s not a RTS anymore, that’s a citybuilder or city simulation with a big blob in the end or whatever.
I mean did you ever rush other players? There’s a huge downside to it in this game. Your army is not in your base so it is unprotected. You don’t only need to watch your base but take a look at the other end of the map too where the rush is about to take place at the same time. That forces you to have a way higher APM and doing a mistake will hurt you very badly. What happens if the rushing player loses 5 longbows to the tc because he was busy building his macro at home? Right, he loses 5 longbows and the defensive player doesnt lose anything because his tc did the job which he didn’t even need to control it. It automatically fired arrows with a 100 % hitrate. No clicks needed from the defending player. And he didn’t even need to build or upgrade it. He just has that defensive structure from the very beginning on. So zero skill involved. Is that fair to you?
I will tell you something: If you lose against a rush in the early game in this game with that heavy defensive orientation, you lost because you met a player that is better than you by a big distance. If he had not rushed you would have most likely lost the game in the late game as well as he might just have a way better understanding of the game and army control than you.