Someone was on TV the other day and said there are not enough people in the UK to fill the job vacancies.
You have to bear in mind that:
1. We are really shit at training people, and indeed reluctant to train people, even the likes of sufficient doctors and nurses, as it (shock horror) costs money.
2. Some jobs require qualifications that are relatively scarce. You can't set Dave from the Council Estate with his GCSE in Art (or whatever) on as a brain surgeon or an engineer. Or many other apparently 'lesser' jobs. Again, are we willing to pay to train Dave to the point where he can get a useful job? It costs money, so no.
3. Many of the people not in work are literally unemployable. Most people do not want to employ crackheads and the like, and I don't blame them. OK, you can in theory rehabilitate people but again this costs money. Also, you need scarce specialist labour to do the rehabilitation. The Tory solution of cutting benefits simply turns these people to crime, or to more crime than they already do.
4. Probably some disabled people could work who don't but once again, it costs money to provide for their specialised needs and 98% of employers just can't be arsed. In theory, you are supposed to make 'reasonable adjustments'. Yeah, right. If the Government invested in these people in a positive way instead of slashing their benefits on a random basis, you might see a change.
5. A very large proportion of the population (in historic terms) is retired. This comprises all the people above pension age (bar for a small minority of very keen types, or people with insufficient pensions) plus all those above about 50 who have decided they have sufficient income (from whatever source) to fuck work off. This includes many with private pensions. As a retired person myself, I can tell you that nothing would persuade me to work again, beyond the small amount I do on my own account when I choose. Not £500,000 a year, let alone a few paltry tax advantages. Absolutely nothing. Many are of similar mind, not least because Covid made them realise that working is not all that and that other things matter more.
As a country, we need to up our game, and in particular, we need to massively improve the education system (note improve, not try to replicate Eton in 1911) and invest hugely in training and career development. And when you've done that, and turned as many jobs as possible over to robots, my guess is we shall still need substantial immigration. Like it or not.