My parents separated when I was 5, which I can't even remember, got back together when I was 6 and moved abroad shortly after, then separated again when I was 7 and my brother and I returned to the UK with my mum.
In hindsight I had a somewhat poor childhood. We were badly off and my mum didn't cope well so I was somewhat neglected. Though I seemed to thrive and didn't think of myself that way when I was living through it, looking back it was poor and I can see that I was one of the kids teachers worried about. We qualified for free school meals but I wouldn't take them because they made us sit at a separate table, so I often "went home" for lunch and hung out at the rec. I was out of uniform (I hated it, but also, I had almost no clothes when I was growing), I missed days at school for no good reason. I got on the county hockey squad when I was 12 but my mum couldn't manage to get me to training so I had to drop out. We went without a lot. All sorts of ways in which, had my parents been together, I would probably have done a lot better. Mainly due to the financial situation and my mum finding it so difficult on her own (in large part due to the financial situation). We saw my dad a few times a year, he came back for a few days for my brother's birthday most years and most Easters too. He took us out to eat and bought us expensive presents and every other year would take us on exotic holidays. Very Disney Dad, but never gave my mother a break or gave her the resources to treat us.
But, when I was a teenager, my mum sort of found her feet and got herself a reasonably well paying job and things settled down. When I was about 15 my dad came back to the area for about 9 months and I got to know him better and I'm really not sure I would have been better off if they'd stayed together. He wasn't violent or traditionally abusive, but he was sooo sexist. He was rude to my mum and tried to make me behave more like the sort of girl he thought I ought to be. Wanted me to be well groomed and well spoken and good at choosing crockery and looking after the house. If they'd stayed together I might have been less neglected, but I doubt I'd have a science degree. I'm not sure I'd have strong boundaries with men or a strong sense of agency. I think, overall, my life would have been worse. However, I'm not sure that's true for my brother. I'm pretty sure that my dad's would have been worse if they'd stayed together, probably my mum's too, but she had a hard time bringing up two kids on her own and I'm not sure she'd do the same if she could have the time over. Might well have waited until we were older.
I don't think we can know that lives being messed up by divorce (or parents staying together) is an indication they would have been just fine if the other choice had been made. Sometimes you're just making the best of a bad situation and even though it's going to be bad, the alternative isn't better.