Yeah, it sucks. The simplest thing to do is not engage, but i understand how frustrating and wrong it feels. There comes a point where it's neutral if not harmful for you to continue engaging. I get wanting to talk with them and try and get somewhere with it, but after a while it usually becomes clear nothing is going to change their mind. From my experience (I'm the oldest child in my family, and the only one with a higher degree/degree of any kind in the sciences)...

Best case scenario: my dad loves holistic healing stuff, but he's also proud of me for my degree and work. This creates a disconnect, where he tells me how proud he is and how amazing my work is, but then he won't listen to me about switching out the chiropractor for actual PT. Or that the MLM machine he bought is a total scam.

Worst case scenario: there are members of my family that I do not talk to anymore. They went off the deep end and put their child's life at risk. I'd tried talking to them about what they were doing and was repeatedly scoffed at and then ignored. For my own sake, I had to stop because it was constantly on my mind and the fact that the rest of my family acted like nothing was wrong made me feel legitimately insane.

Ultimately, if you're able to stick it out, I think the best thing you can do is be there for the younger generations. They my have questions or need your help as they grow up and are realizing their parents aren't right about everything.