OP I'm going to disagree with most people on this thread. I had a birth which was like yours interventionist when I'd rather not. I've read quite a bit of Sarah Ockwell Smith's stuff. She's not a great writer in my opinion but the research she is referencing is valid.
I think she's also quite brave to talk about things that are a r Al taboo (like feeling differently about different children, for whatever reason). I've also read quite a bit of Michel Odent's stuff and done his doula course, mainly to get my head around what happened at my birth.
There's lots I could say but first and most important is to note that kind of birth you had can trigger PND. It's not surprising or usual that that might come up later, your body and mind prioritises your baby at the start, the darker stuff often doesn't surface until later when you have a bit of spare capacity.
Please, please though, don't feel 'crap' as in, if I'd done better birthing, my baby / things would be better. That's not it at all. We all, especially first timers, birth in a system which sets us up to fail. What's more surprising, in the current model of standard care, is that quite a lot of people do manage to birth straight forwardly, rather than how many don't.
Rather, maybe, see this as the beginning of working through what the birth opened up for you. And/ or getting and making the changes you need to come to terms with it. How well you are , both emotionally and physically, matters a lot, and looking after yourself is the foundation of being a good mum and looking after your baby.
For me, the process took about 18 months and involved both understand the practicalities of what happened at my birth, and working through the emotional side. We had the support of a wonderful post natal doula who made a massive difference. I saw a wonderful cranial osteopath for DD regularly when she was little. I knew some of her more difficult aspects where connected to her birth. It helped some of that, some of it I rode out with her.
And I prioritised working through what it had brought up for me, as much for her and my subsequent children as for myself. I had a debrief with my obstetrician, I did a birth trauma session with our doula. Then later I did some therapy / counselling (not about the birth so much as working to heal the less constructive aspects of my personality that it revealed). And then the doula course with Michel Odent which has completely transformed my understanding of birth (and I thought I was well informed before) and made me excited and confident to do it again (and where and how I will).
In the end, although I still regret some aspects of it, I value the insights into myself it has brought. Through it I'm making changes that are benefitting me, my relationship, and my daughter. Though these have not always been easy.
The 'all that matters is a healthy baby' arguments are tosh in my view. That is a very low bar for success, and minimises the many many women who were upset or bothered or traumatised by the birth experience, and encourages them to ignore very valid feelings. Yes birth care is much better than it was. It's also a long way fro.m what it can and should be.