Unfortunately the British also fielded some of the most incompetent, muddle-headed, or over-promoted commanders of the war as well. (e.g. Percival, Mountbatten, 'Bomber Harris'...)
And then there was the whole tank fiasco.
and yet, despite all those handicaps, somehow, they 'won' (or at least didn't loose) ..
Which says (to me) that there's little way for the Nazi's to do any better i.e the British are already as bad as they can be ...
... there are, perhaps, some tweaks that let the Nazi's last longer , but the big changes means they are no longer Nazi's ..
[here's one tweak - the 4 rotor Enigma gets introduced earlier ... and then some-one points out that the cost of the machine with it's entry ring, the 4 swappable rotors and the 'reflection' ring is the same as a real 6 rotor machine, so they get rid of the complex 'reflection' bits (which was what prevented a character encrypting to itself and is the flaw that allows the machine to be cracked) i.e. they introduce a version that can't** be cracked]
**EDIT with the technology of the time and assuming they use it correctly (i.e. no insane encrypt the 'start key' twice .. or use the same start key twice wit the same day settings
NB. don't get me started on American tanks (USA SHOULD have been churning out Sherman's in 1940, what they had was that abomination the M3 Grant, which is essentially a knock off Char B designed in the 1920's (ie. the early one with the thin armour, not the one that the French eventually built after 15 years of ditherrring)