Thor is the only MCU character to have shown City level feats, and even them most are debatable, uncertain or done by Chain-Reaction and other factors (Sokovia's feat was done by hitting the Vibranium Core, and Thor had to charge his strike for a few seconds.)
However, he is shown time and again to capable of being hurt by the likes of Hulk, Ultron and even Iron Man (Barely). Those characters are all at far weaker in power. Even with Hulkbuster Iron Man is barely Building level, and Hulk is at a similar power.
It is illogical for Thor to have City level AP and Durability, and still be shown to be at comparable, if not smaller levels of strength than The Hulk. The Avengers movies follow the philosophy of a "Balanced Team", and this translates to everyone having Average stats on almost everything sans one thing.
I.E, Hulk is the Strong and durable Guy. Captain America's shield is made to be the best defense, enduring even Thor's hammer, Quicksilver is the only one with Fast Combat Speed, Scarlet Witch has powerful magic and mind manipulation, but is an ordinary human otherwise. Thor is powerful, strong, but is still made to be slower than Quicksilver and capable of being harmed / pushed back by Iron Man's tech.
If we were to have Thor at city level, literally everyone in the MCU would be scaled upwards for the battles to make sense.
We'd have stuff like Small City level Whiplash and Iron Man... And let's be frank, that isn't the case whatsoever.
Unless City level feats start becoming common later on for other characters, we can't use Thor's.
