Two of Windsor Castle
I think context would have been nice. More elements in your composition... foreground objects, etc. I do agree that these feel a bit like snapshots that anyone could have taken. Try making more of an interesting composition next time. Use leading lines, framing elements, foreground objects. You want to give reference to where these buildings are, how big and grand they are, and the beauty that surrounds them. It's not exactly easy to get everything right when you are just passing through while on vacation, so I understand. Heres an example of what I mean...
(not my photo btw)
|Black on White by RaVN11|
|Hummingbird and Bee by dibilio57|
from A Big Year - birds
|xheneta iseni _for DPReview by Mike Slade|
from - My Fair Lady - (Portraits in Full Colours Only + A Border)