I grew up speaking the lingo and save university and a couple of college courses had all my education in it as well.
Always felt it vaguely bemusing it ruffled so many people’s feathers, particularly Welsh people of a certain age and perspective. I’d say from my experience I don’t think I’ve met many under the age of 30-40 now that aren’t either positive or just agnostic about the language in Wales. I think it’s becoming increasingly normalised.
I’m a big advocate of language acquisition though and a lover of languages generally having learned (well, learning still) another two to varying degrees of success. I wish we pushed this more in British schools more broadly for languages to be taught consistently from a really young age, regardless of what that second language is. When the time comes and I have a child, and should I still be living in London, I’d seriously consider a school that does this even if I or my partner don’t speak the language.