I was about to reply in the same manner but came across yours first. I agree completely.

I don't think it's appropriate but appealing to the OP, I would say for your own sake it's a giant can of worms to get involved and try to take on the role of counselor to your parents. It's not only already a complicated situation to have to counsel married people even as a third party but add to that that they are your parents therefore you will have a bias of some sort or many on both sides and it won't be effective, your emotional stake here is too much to be an objective adviser. The other thing is even if you were capable of being objective and entirely unbiased in the situation it won't seem that way to the party that seems to be more criticized than the other and mind you one parent/side WILL appear to be more criticized. it's inevitable. You risk alienating yourself from one or even both parents by getting involved tbh.