If we won the Euro's this Summer and beat Estonian away 3-0, and you'd think we'd complain
Depending on the performance, I don't necessarily think there would be no complaints.
Not saying that there would be complaints, just that you couldn't rule them out.
Anyway, the middling nations have improved, undoubtedly. Yes, certain aspects of their game are weaker - squad depth, pace, stamina would be three that I'd highlight - but by and large you've got teams that are now professional, players with reasonable levels of experience and managers that can get them organised and disciplined.
The micronations - Malta, Andorra, Leichtenstein, Luxembourg, Faroes, San Marino - will always struggle due to their tiny populations but even then we've seen wins against rather big nations from one or two of them.