Britain has a sad history of stupid, blundering command. My theory is that their officers tend to be aloof and stuck in pre-set tradition.
Anyway, I’m with you about not getting too excited about Dunkirk. Dumbkirk.
British dumbness was rescued by Hitler’s greater blunder.
Whilst it is true that Britain tends to glorify its great military disasters more than it does its victories (charge of the Light Brigade, Dunkirk, the Glorious Glosters etc) you are being overly harsh on the Brits.
The British were no dumber when they first came up against the Germans in WWII than any other nation, the French, the Russians and even the Americans (Kesserine Pass) all got their asses handed to them on a plate when they first encountered the tactics of the Germans.
The point is whether the generals learned from their mistakes, and despite the caricature of British generals as all being stuck up know-nothings the fact is that they were quick learners and generally tended to win the wars they get involved in, even if they did stuff up at the start.