My own personal experience of aging is that the opposite is true. Young me thought in very black-and-white terms and knew everything. I now live in the grey and although I find it more difficult to deal with new ideas (partly because of age, partly because of the grey), I’m a lot more open to those ideas and willing to give them serious and fair consideration. YMMV, but a blanket statement that old people generally are stuck in their ways doesn’t match with my personal experience and when I think of the old people I know, to the extent that it’s true it’s true for a minority.

The referent as it relates to science probably has to do more with corruption, incentives, and careers being built on certain ideas and having pre-existing knowledge rather than anything specifically age-related.

In any case, whatever longevity treatment is applied may actually reverse or reduce whatever part of your claims have some physiological truth. It could mean more wisdom and less curmudgeonry.

New ideas aren't always great ideas.

And to counteract it, a sufficiently long-lived humanity might actually have to deal with the consequences of their own actions. Right now, there's quite a lot of folks who are of the mindset that they'll die in ten to twenty years, so why should they care? It's a generational pass-the-buck.

here is an idea: age weighted voting. starting at voting age, give every X years interval Y% votes.

if there is a lot of old people their vote matters less. if there is a whole lot more younger people their vote matters less.

i’m sure this would work great. also sure i’m the first person to have thought about this. /s