I agree with you. The ideal being to write well and fast.
Personally, as a non-native english speaker, i'm striving each day to write more words. The 3 to 5k words recommended here. But not by sacrifying more time. Even i can write 5k words with my broken english if i don't care about anything in 2 hours, but that would be bad.
Today, i can barely produce 3-400 words an hour at my best english. And i have an almost finished outline for my story, so no writer block at all. I lose time searching for words or checking grammar rules, but i'm quite unfocused. I could probably step up my game to 700-800 words an hour if i was more efficient.
In the end, i'm quite happy if i have 1500 words written at the end of the day, but with time i'm confident both my english skills and writing speed will improve if i keep the good work. But only if i write. So writing more is the good way i think, as long as it's done mindfully.