This has been playing on my mind for years. It's all so easy to bash PILs. It seemed to be an accepted thing when I was meeting others mums with DD1 that it was fine to roll eyes about them, lament them coming for xmas, curse what a bad job they're doing with babysitting, say what a nightmare they are. I know people who actively try to discourage their partners relationship with their parents. One even who told her husband that now they were married her parents came first!
I always got on with my PILs, one more than the other although I respected her as ExH's stepmum. We got divorced last year and I guess I appreciate one set of PILs more now the others have dropped me like a hot brick Yes they all pissed me off at times but they're only human and typically therefore especially as a mother of a son, it must be hard to 'lose' them and not intervene in his relationship when there are arguments or you feel they're being mistreated. I've seen it with my sister and her idiot husband and I know it's broken my parents' hearts.
Just putting it out there as it's less often said.