Regrdless of their professional level, when the brits, and all the other english mother tongue, will be able to manage a second, third, fourth language(s) at a decent level instead to talk with non english mother tongue as the only truth holder I'll have higher level of respect to them.
The language of ATC is English whether you like it or not, if someone wants to speak a different language they should work elsewhere. If you accept that then part of speaking English is pronouncing it properly.
Brits may appear arrogant in their lack of linguistic skills but are by no means alone as I have found throughout Europe, including Italy. That English has become the language of aviation and certain other fields is an accident of history I will not apologise for but I see an arrogance in your post that stems from your linguistic abilities, that is NOT an accident of history.