Hey. I see you around on TSR quite a lot asking similar questions to this but felt too afraid to admit that I feel the same way as you very often. I've never felt so low.
I'm also in Y12 and all of my friends do STEM- I achieved the highest GCSE grades in my school and now I feel like I've done nothing since, and I cry through all of my online lessons in regret and shame and my sleeping problems have just intensified (and I can't believe I'm not using the anon feature to say this but I felt bad for you and so wanted to say something).
No, people who do English are not stupid- of course they're not and they tend to be intelligent in other ways- and no, of course you won't end up completely dirt-poor either if you work hard, make the most of university, gain experience, work part-time, try and gain leadership positions in societies or unions. At least, this is all the advice that I have gathered from my time on TSR. I'm still in school and so have little knowledge of how things really work, though I try my best to find out as much as I can as early as I can.
TSR is also guilty of 'STEM snobbery' (I'm really afraid that saying that will start an angry heated debate later on in this thread, but it's necessary to mention). I can definitely say that my insecurities around English were partly worsened by this site (though this site has also been so helpful to me in other ways). Remember that most of us are just students though who have no real experience of the outside world nor have they contributed to these hailed 'research developments and areas' that STEM is praised for. In fact, these sectors are supposedly over-saturated anyway. I wouldn't know for sure. I guess it can be argued that neither is better than the other, though the arts and humanities require more work, effort and initiative to increase employability post-graduation to get places. It's not like science students don't get industry/work experience and some fields require a masters to even get a position (like Chemistry, apparently). Even med students have 'work experience'- it's just that their hospital placements are necessary for their course and for passing, so it's automatically integrated into the degree.
Your other worries are valid, and they're also mine. I work much better with contact hours and in classes, having discussions or being able to ask questions and research as a group, so realising that English has little of these has made me anxious about studying it at university. I simply don't know if I'll love it beyond sixth form, which is why I'm worried (I've done a little research into the course and I really am not sure what to think about it). Also, as more time passes, I'm starting to realise how I do miss the structural, logical nature of the sciences that I can only slightly experience nowadays through A-Level Psychology, the closest I even come to a 'science'. In short, I wish that I'd taken a mix and enjoyed both the logical and critical thinking aspects, not just one or the other.
It's not the end though. I've been talking to friends and to people on TSR, and they have presented me with a few options if you're really regretting your options this late into the year.
1. Take a gap year and study A-Level sciences independently (though I'm not sure how practicals can be arranged- through a college or tuition service, maybe) and then apply to university. I can also get work experience in some fields if I want.
2. Start studying a science now in time for Y13 exams- since I already do Psychology and have recently started to gain some interest in Medicine again (a bit late for that, haha), I've been told that I can combine Biology and Psychology for some med schools (I think there are ten to choose from if you try this way, and prestige doesn't matter at all for med schools). I have friends who are willing to share their revision resources with me, and I might have to beg the science teachers to let me do practicals or catch up enough independently to request rejoining in Y13.
3. Leave for a college and restart the year- I don't want to leave my sixth form though, so I personally don't want to do this. I'm not sure if it's possible to restart in my current sixth form, so I'd have to ask.
However, please ask yourself if you really want to not do English because you're not sure if you'll enjoy it anymore or purely because you care about graduate prospects before you do anything. I might take a gap year and decide whether or not to do science A-Levels then because I still want to make sure that it's English I really want to do or if it's scientific research as a career (specifically medical-related, as that's what's recently gained my interest. But I change a lot- one moment I want to teach English, the next I want to work in politics, and the next I want to work in a lab. If only we weren't forced to specialise so young or if IB was a choice).
It makes me so sad to see you upset about this (like I said, I see you a lot around TSR posting similar things to this but have never said anything). I can really empathise with you. You're not stupid. We're not stupid. I think we're both just afraid. I hope you'll be able to figure this out. I'm contemplating talking to my teachers about this to sort things out because I'd rather improve my situation than cry through all my lessons. Good luck, and sorry for the long post.