Well there are two issues here:
Firstly, method of delivery. I don't think 'university' itself is necessarily the problem. After all, even tuition fees are capped at 9K a year.
It's the expectation that people go away to study, for 3 years, often far from their homes. Racking up accommodation, food, etc costs. It's a somewhat British approach to expect them to go away, in other European countries with cheap university education most students live at home and commute.
In relation to the first, tuition fees and supply of grads. Opportunities were opened up for the first few to go to university, because it didn't cost them much provided their achieved, and jobs were plentiful. Tuition fees were introduced only in 1998 by the Blair government with students paying up to1K.
In 2024 it all costs a bomb. Not only that, because there are so many graduates plenty of jobs that previously didn't require them, insist on degrees. In my field many of the old-timers worked their way up even form clerical grades, this is impossible nowadays.
The plum 'graduate jobs' require multiple rounds of interviews, tests, etc. Graduates who need to work to fund themselves are less able to prepare, similarly many academic kids have to opt out of courses where the workload is too high as they need PT jobs. This isn't just 'low-income' people but, for example kids who have siblings in university at the same time... parents expected to make up the shortfall but don't have the money.
It's becoming more like the US, but what people forget about them, is that community college and state institutions are heavily subsidised for residents! The massive student loans etc are for people going to other more 'prestigious' institutions but it's possible to get a cheaper degree.
We have the OU, part-time degrees etc here but they're still not as cost effective or even sold as a viable option.