I think I have a different experience to a lot of people i know. Many of my friends are like the people you mentioned - they hated it, it felt lonely etc.
That was my exact experience in my first year but since its been much better. However, i cannot stress this enough DO WHAT YOU WANT. University is 3 long years of independent study & coursework. if you do not have the motivation you will hate it. I would strongly suggest taking a gap year get a job.
I also think university is a good 'sandbox' time for many young people. Personally, if you threw me into the world of work at 18 i would have failed tremendously. Uni is a time for me to learn about myself and grow my self-confidence. Me now vs me then are two completely different people.
I would advise going to uni if:
a) you really like the subject - and to make sure you do plzzz do a lot of research (google the uni course, look at the lectures and read some of their work/published articles, and try contact some students ask for their perceptive and if possible some of their lecture slides)
b) You are not too confident in yourself/abilities and/or just need more general time to figure things out. I don't know why people think the moment you turn 18 you are a fully fledged member of society. Adulthood is a process and some people need a couple years to adjust.
c) Your desired career plan requires a degree
In terms of expensive/enjoyment/lonely. These are extremely situational and not everyone's the same.
Enjoyment/lonely is what you make of it. If you try to make friends you will not be lonely. If you stay in your room all day and not go lectures then you will. Same goes for enjoyment.
As far as expensive - they can only be fixed through preparation. Do a budget see how much money you get, see if bursaries are available for you, uni jobs at your uni. Up north tends to be cheaper, rural unis have cheaper rent etc... The only people i know who have struggled with money are those who had a lot and went crazy spending it all. and those who did not even think about it and thought they could deal with it without preparing
I would also like to point out doing a degree you hate/fail at is worse than doing no degree. SFE only funds 4 years. So imagine you do 2 years and realize you want to do a different degree or something.