Most UK towns have a mall, my city has typically had three, although it can't support three, what happens is they build a new mall, the oldest one loses all its occupants and takes on desperate clients like e.g. an entire floor is just discount no-brand furniture, or a factory seconds outlet, eventually it goes bankrupt, closes, they tear it down and... build another mall, rinse and repeat.
The last decade or so though they realised ah, that's not actually a sane plan, and the city council started demanding they provide a plan that can actually work before issuing permission, so e.g. the big mall in the city centre had originally planned a huge extension full of new stores, they realised there is zero demand for that, so they pivoted to it's a nice cinema, plus restaurants, and some residential on the side.
Meanwhile the last mall site went from "We're building a new mall" to "A new mall... and residential space" and then "A residential block, also there's some retail on the ground floor" as they realised that retail space is not going to move. Residential isn't as profitable, but "£5k profit selling a £200k new home" is a better deal than "Ongoing loss on a £1M retail space you can't sell".
The UK government changed planning laws some years back to encourage commercial to residential conversion. If you wanted to build a new residential building with shitty paper walls between homes, third rate insulation and not enough elevators, you'd get told "No". But if you want to convert an office block that is now useless or a shop that hasn't been rented for years, that already exists so the planning restrictions are fewer, maybe you put a little bit of extra insulation in, you run some extra plumbing, but you don't need to meet new home standards, and people get a "new" home that kinda sucks.
The result is that a lot of what you're talking about as "High Street" (the US has "Main Street" filling the same role) was converted to housing. There's a row of shops not far from me, ten years ago the upper floors once used as office space or for storage became housing, this year the shops closed and are boarded up, they'll tear that out and make them into more housing. A pub I used to go to regularly was converted to nasty poorly put together flats in the same period.