I'm late to the party, but I certainly don't think charity shops have had their day.
I have still managed to get items of clothing for less than a fiver, and I'm gobsmacked on some of the posts claiming £25 for a faded Per Una top or £10 for a bobbly Primark one. I wouldn't even buy anything from Primark new because their clothes are not made to last.
I live near a University city, and the charity shops in town are always busy with people from all demographics. I would also point out that some plenty of people will not have a Vinted or eBay account especially if they don't own a smart phone.
There are two closer to where I live, and I suppose, they are what most of the posters on here would call "proper" charity shops that charge only a couple of quid for clothes. I saw a pure silk Reiss top for £1.99 the other day in my size, and I have in the past bought Denby items there again, for a couple of pounds including a tea pot, sugar bowl, and milk jug, when they were having a half price sale.
I used to work in the other one, and they really do charge very little for their stock. I had a lady who paid 10p for a ball of wool, and because their wasn't a price label on the other in a different colour, I said 15p and she challenged me on that! Some customers really do want something for nothing! Some lucky person managed to buy a Hermes scarf, in its box for £15, but did try to offer more money for it.
Re volunteers taking all the good stuff: yes, we get to see it first but the rule was, it needed to be out on the shop floor for at least half a day before we could buy it ourselves. The discount was 25% then.
I use eBay and Vinted of I am looking for something specific, bit sometimes of I have the time, it's quite satisfying to wander into a charity shop and find a quirky item for a few pounds.