Rating every civ’s architecture seems a bit much, but I know a reasonable amount about English medieval architecture (for a non-expert), so here’s my assessment of Britons:
Dark Age: Not very appropriate. The cloth/hide roofs in particular don’t resemble anything I’m aware of from medieval English architecture. They should probably look something like this:
(These are reconstruction Anglo-Saxon buildings from around the 7th/8th centuries.)
Feudal Age: Generally very appropriate – timber-framed buildings with thatched roofs were very common in England throughout the middle ages. My only nitpick here is that the Feudal Age is probably too early for the jettying seen on the barracks.
Castle Age: Generally, these buildings are very appropriate. The monastery includes Norman Romanesque and gothic elements, which is very common in English churches, although you wouldn’t build one from scratch like that. The sudden absence of thatch is inaccurate – but it makes sense as an artistic choice, to show some progression through the ages, and the tiled roofs are perfectly fine. The lack of a market cross is a bit weird.
Imperial Age: Things go downhill here, since the buildings that change (town centre, market, university, keep) don’t really resemble anything from medieval England. They look somewhat like Georgian-period architecture, but that’s well after the AoE2 time period.
The wonder is either based on Chichester Cathedral (weird choice) or is supposed to be a generic English cathedral. The overall layout is correct, although it looks awkward crammed into a square, and the orientation doesn’t match that of the monastery. There are several features that look pretty off, the most conspicuous being the slate roofs on the spires.
So I guess probably 7 or 8 out of 10? (Although I’m not really keen on assigning arbitrary numerical scores to things.) Since Dark Age is short, most Castle Age building graphics carry over into Imperial Age, and one hardly ever builds a wonder, it’s mostly very good.
But with the topic of this thread, you’ve set up the perfect conditions for extreme negativity! In fact, didn’t you partly do that deliberately, so you could voice your own negative opinions about Armenians and Georgians?
This is really not a reliable method here. We’re talking about buildings from 500 to 1500 years ago. Buildings that old rarely look the same now as they did then – either due to modifications, inaccurate restorations, or generally falling into ruin.
You’re free to base your opinions on whatever you like, but if someone else has some more specialist knowledge, I don’t see the problem with them sharing that. In fact, that’s what I’d hope for in a thread like this.