Hey
Sorry to hear you're feeling like that.
For reference, I am speaking as someone who started one course at one university and then left after about 6 weeks. This was due to not enjoying the course and then when I tried to move course unfortunately the university made everything very difficult (saying yes then no) and stringing me along for weeks on end. That's to say I know the feeling when things aren't working out how you expected and it feels like no one else really understands.
For me, there's a couple of things to think about here. As some people said when I was struggling, it is only 3 years. It sounds crazy because that's still 3 years which is a fair amount of time. But if you're starting second year then you're already half way through. Especially if you have made friends and don't mind where you're living and the life you've got there it might be worth hanging on in there and seeing it through. Saying that, I also know that if something doesn't feel right, even after you've giving it a decent amount of thinking time, then I think you should trust your gut. Just make sure you organise yourself if you do leave and make a plan so you have something to work on and look forward too even when it sucks for a bit.
The other thing I want to address is the Russel Group university point. Personally, I find it frustrating that it is such a big deal whether a uni is RG or not. It is all based on a very old system regarding whether a uni produced a certain amount of award winning research. For reference, there are universities now such as University of Lancaster which is ranked really highly in a bunch of the uni awards and is producing some real cutting edge research, plus it has higher student satisfaction rates than Oxford and many other prestigious unis yet it isnt RG. To me, I think we should be valuing the important things such as how happy we are as opposed to a system which is around a century old but anyway...
That's not to say I'm aware than unfortunately where you get your degree does still hold some weighting in the world. However, I would prefer to have fun and work hard somewhere not RG than try really hard just to try and fit in at another uni because it's supposedly better.
Apologies if that's a bit opinionated and blunt but I think it's worth thinking about. I do know quite a few people with good degrees from non-russel group unis and I don't think any less of them.
Do what you think feels right, we're adults now and unfortunately, no one is going to make the decision for us.
But sometimes that's a little bit exciting too
Hope this helps