Maybe I'm being really U, but I find the 'no parent is perfect' thing a bit annoying.
No parent deliberately does a bad job. But some parents DO do a bad job.
If you experience an unhappy/neglectful/abusive childhood, the parent(s) may well have been doing the very best they were capable of, but that "best" was insufficient.
Or (more likely) the parent didn't actually do their best - they did what was easiest for them, or half-arsed their best, or did their best sometimes, but not always. But when/if questioned, they will claim to have "done their best" and squawk that you are demanding "perfection".
So I guess what I mean is that;
a) there is a minimum standard of parenting, and that is outcome-based, not effort-based. So if a parent does their best, and their best is not good enough, then they were still a not-good-enough parent.
b) Parenting is NOT divided into "doing my best" and "unrealistic standards of perfection". Those aren't the only two options.
If you are a parent, and there are areas you feel you could improve on, it is OK to act on that feeling and make changes to your parenting. the thing is, as soon as a parent ventures to say "I feel maybe I'm not a good enough parent" everyone hastens to say "OMG you're brilliant, just do your best, no one's perfect" because there's such a strong taboo against criticising anyone's parenting or implying that parents aren't all 100% amazing superheroes.