Hello OP
I started my career off in the social sciences and now I teach in the sciences. It's a bit of a long story but I have experience trying to publish in the social sciences.
When I was firmly in social sciences I could've written your post. I used to find writing social science papers incredibly challenging because of the level of theoretical engagement that was required. Obviously I was mostly on top of the theory in my area but I found it so hard to boil the huge range of theoretical insights down to discuss them effectively in a 2,000 word literature review in a paper. As you said, incredibly intellectually challenging.
I also didn't really get the point of it, to be honest. It very often felt like naval gazing, citing the right people just for the sake of it, and leading to quite unadventurous and uninteresting papers (because you pin your data/thoughts, basically, to what others have said before rather than thinking creatively about data you might have).
Like you, I too found myself getting worse at it as I progressed because I would second guess reviewers and keep going back over my work. It took a lot of work to train myself out of that habit.
Since moving out of the social sciences (I do still try and publish in social science journals but I don't have to), it's a different world. Where I am now doesn't require the same degree of theoretical engagement; you obviously have to review what's gone before but this doesn't seem to be as parochial as in the social sciences. I guess my papers now are more "descriptive" than theoretical and wouldn't hold much weight in social sciences but that's the way I enjoy writing and communicating my work.
Remember that the peer review process is completely shit too. The anonymity means people people are free to be as horrid and dismissive as they like. This is, in part, because peer review isn't paid so people are trying to squeeze this in around their other tasks and don't have time to think about what they're saying and how it may come across. Plus, academia is also full of arseholes who like being mean. I also think editors are terrible nowadays at failing to desk review papers (i.e. sending stuff for review which then gets torn apart- WHY? Just reject it straight away with some broad suggestions for improvement), and failing to control reviewers (i.e. telling reviewers their comments are too harsh). Again, I think this is partly because editorships are being done around other work commitments. I actually found it really helpful to follow @shitmyreviewerssay on Twitter, which is where academics basically share the awful things reviewers have said to them. It helped me feel less alone and less dumb.
I also found it very helpful to co-author where possible. Bringing other people onto papers not only shares the load of writing and editing but I also feel like it shares the misery when I get rejected and shares the responsibility for doing something about it. When I co-author, I get a lot of confidence from sending rejections to co-authors and them not saying "well, yes, of course it got rejected, you're shit". When they come back with "Ah, that's a shame. Why don't we try Journal of Such and Such next?" I feel like the rejection is kind of neutralised. OTOH, when I get a rejection on a sole-authored paper, I internalise it and dwell on it massively.
Can I ask what stage of your career you're at, OP?
Are there any mechanisms for peer review at your institution?
Don't forget too, that if these rejections are recent, there's a massive REF panic going on and journals are being a lot more selective in what they're putting through.