I feel this all the time, especially raising neurodivergent kids. A lot of what looks like bad parenting or letting things go or whatever in any one moment is often part of a really complex series of decisions and judgement calls based on a huge number of factors.
“Is that parent really a total idiot, or does (s)he perhaps know something about his/her child that I, a total stranger, do not?” is a question worth considering, much of the time.