I think that immoral is a rather strong word, yes. While I woldn't say that it is "just" about debauchery and lust, I dont think that the weakness and selfishness of the Prices OR the Bertrams is quite so bad as to be immoral. Mrs Norris Im not so sure. She is extremely selfish, mean and bullying... She's downright cruel to Fanny or anyone who can't stand up to her. She sponges off Sir Thomas.. SHe encourages her neices to be selfish...

But the Prices and Bertrams generally aren't that bad. Mrs P is lazy and not very good at things, but she's trying. She could do better, but she problaby just can't make the extra effort. She spoils some of the children and neglects others, but she's got 10 of htem... its hard to be fair to them all when you have a small incoem and a sick husband.
As for Sir T and Lady B, again they are mixed characters.. Sir T is trying to be a good father, even if his worldly side too often crowds out the "good father" and good uncle side... Lady B is indolent, but she's not unkind to Fanny.. she's a non mother rather than a bad one...