Always an All-In? No!
AK is in horrible shape if your opponent literally only plays pocket Aces
Most players are literally that tight though. The other big situation where AK All-In is horrible is when you are more deepstacked. The deeper stack depths get, then the more chips you can lose per hand, so All-In becomes gradually worse and worse of an option.
AK is a great hand for usually value betting, but there are also times AK needs to slow down and play more cautiously. All-In is an extreme for aggression, but it lacks the nuance of poker.