Agree one hundred percent, but I would like to see examples of people being ashamed to be English or preventing it from being celebrated. The only one I can think of is Emily Thornberry's tweet of nearly a decade ago and even then she was pretty much sacked on the spot.
As some have pointed out over the years, it's almost un-English to get too worked up about the flag as one of our qualities is reserve.
The Celtic nations have centuries of languages and folklore in a way that we don't (unless you count Morris dancing...) and this contributes to their sense of national pride and belonging. Even then, one half of Northern Ireland looks to a foreign country and the other across a sea to countries they're not even part of (England and Scotland).
It is good that following the recent Euros there's a lot more debate about what it means to be English and the players and manager have acquitted themselves well on that score, compared to the flag-waving yobs you used to see.
Football is a mixed bag of course, it has the power to bring us together with its tribalistic nature, yet at exactly the same time, and for the same reason, you see these fucking wankers spouting racist bile all over the internet.
I gave up really following football many years ago, partly because of that tribal thing, partly because of all the on-pitch handbags.
True what you say about the Celts, the rest of us (in England) are in effect a diverse mix of Germanic, Scandi, Eyetie and Gallic (and of course these days, African and S. Asian too

), so maybe that's at least partly at the root of it all? But also of course, our colonial background, whether that be constantly invading Scotland, Wales and Ireland, and latterly India, North America and the Far East. What a bunch of gallivanting bastards we are! And we are, rightly or wrongly, constantly getting digged at over that past.
I guess you might almost put it on a par with Germany after WW2, they only really stopped constantly apologising for what happened after about 2000 (while of course in the intervening 50-odd years, easily overtaking us in the industrial stakes).