OP here. Lots of different opinions and experiences on this. My own experience was pretty atypical I think, but I thought I would share it anyway. Before I begin, I want to make it clear I'm not trying to trash either of my parents but that I'm just trying to be honest, as honest I can be from my perspective.
I'm the youngest of 3, currently in my early 30s. From what I can tell, my parents had a good marriage for maybe about 6 years, then an okay marriage for another 8 maybe, and then it was pretty bad from then on. We (my parents and I; we all three get along fine together now) recently watched a bunch of old home videos starting from only a couple years into my parents' marriage, so I feel like I have both the perspective from when I was a kid and looking back on things as an adult now. There were always problems in the family, but I remember us being relatively happy up until the mid 90s, then things started going downhill. Both of my parents changed a lot, but my mom changed an enormous degree and developed into a really miserable person to be around period, let alone have as a mother or wife. I'm not really sure what happened, but she also become kind of literally crazy, not in a haha way, but in a way that is profoundly traumatizing.
There were other things going on too, but I think being married to my mom caused my dad a lot of stress and grief, and it absolutely affected him and what kind of parent he was capable of being. My mom just kept getting crazier, and my dad didn't cope well and became pretty miserable and difficult to be around also. Some of that was just him, but stress and unhappiness made him more and more short-tempered and irrational, and I don't think he was really able to be mindful of his kids' emotional needs because of his own emotional state. I vividly remember being in high school and dying for my dad to divorce my mom, and I still to this day know my life would have been exponentially better had my dad divorced my mom sometime between 2004 and 2007 instead of waiting until I was out of high school and off to college (divorce finalized in 2011). As it was, the divorce didn't affect me at all and wasn't surprising to me at all. My mom was somehow blindsided, and it devastated her, which I felt sorry about, but truthfully, I was happy for my dad and told him I didn't blame him. His life improved so dramatically after leaving my mom that it would seem bizarre to me to hold anything against him. He got a new girlfriend after a couple years, and even though I never connected with her and they even broke up about a year ago, I'm still glad he had that relationship in his life as it really revitalized him in a way. He was happier, more outgoing, made lots of friends, and all around just started living more. My mom never really recovered fully, but in all honesty, the divorce was good for her in a way too because it forced her to apply herself in life some, and her self-esteem is probably the highest at present it's ever been in her life, and she's much more functional than she was those last 8 or so years of marriage.
Getting back to the original question, I can tell you with absolute certainty that divorce was better for all involved (with the possible exception of my mom, but that was due to her own actions and attitude), it did not negatively affect me at all other than the normal stuff you have to deal with like splitting holidays etc, and I wish the divorce would have happened sooner. I can't say how it would have affected me if it had happened when I was a small child, but had it happened when it probably needed to (probably 5 years before it finally did), it would have freed me somewhat from being around my mother, and it would have dramatically improved the quality of parent my dad was capable of being. I recently told him I was dying for him to divorce my mom in high school, and he said the only reason he didn't was he was afraid of how it would affect me.
Divorce happens for many different reasons, some of which are not justified. If two people have kids together and parent well together but just don't feel passion for each other, I'm not sure divorce is justified, at least when the kids are young. If the relationship is toxic, however, especially if it's bad enough that it affects the quality of parenting one or both parents can give, I think divorce can be and often is the better of two evils. I have never been married, so take this with a grain of salt, but my own opinion, taking some from my own observations and (non-marital) relationship experience, is if you are seriously considering divorce as an option, the marriage is already dead and likely has been for a long time. It is easy to stay in okay relationships. It is not easy to stay in bad, toxic, dysfunctional relationships.
Just my experience and two cents.