While I agree with you and also agree with the decision to not show it anymore, I do want to highlight this bit that you wrote:
instead dad physically abuses the misbehaving child and nothing is ever resolved
The positive thing is that it never (or so raraly that I wouldn’t remember) presented the strangling as anything good or helpful. Instead it was always presented as a shortcoming of his personality. Homer is mentally ill equipped to solve conflicts with Bart non-violently. Strangling him was his only outlet and (at least to attentive viewers) it was clearly and evidently damaging Bart’s development. This is for example demonstrated in a scene where Bart has such a trauma that he’s getting “strangled” by thin air when he thinks his dad would go for it.
Also, with the knowledge that Bart is, to some extent, Matt Groening’s self-insert, that does raise some rather unpleasant questions.