I dunno. There was definitely a time, not so long ago, when I'd have agreed 100% with the op, but I think the high street is in an absolutely dreadful state at the moment, and that goes for pretty much any price point.
Take my go-to everyday outfit which is normally jeans, T shirt and then some kind of tailored jacket/blazer in wool, tweed, linen etc - it can be mannish and oversize or vintage and fitted, I like both. So I agree about high street jeans. My current favourites are from the last Uniqlo / Jil Sander collab. M&S ones have also been ok. High street T shirts I'm less impressed with. I buy them there because I'm fussy about style, neckline and colour and prioritise that over quality, but it shows.
But the worst is tailoring. As soon as I pick up a high street blazer I can tell by the weight that it's going to be crap. So I only buy second hand designer (Margaret Howell, Joseph, Max Mara ) or vintage (any decade up to the 90s) and yes, it's miles, miles better, even if you might be pushed to spot the difference on Instagram with the right lighting.
Something has gone badly wrong. We used to be good at this. It was our bread and butter.
As to whether dress sense is innate, I'd say it clearly is for some people but I disagree that it can't be learned. In most areas of life I don't have great visual sense but I'd say I've acquired a reasonably good eye for putting clothes together, purely by watching other people, both in real life and on screen and in magazines, and by trial and a hell of a lot of error.