Old? You're hardly even middle age! Someone who is actually on the later stage of their working life might take issue with you calling yourself old.

I'm sorry that the jobs you've hit up made you feel old, but please keep in mind that that is more a property of the places where you've interviewed rather than a property of you. Plenty of places will have interviewers in their 40s or 50s if that's what you're after. Maybe start looking at more established organizations rather than the nimble upstarts?

It's probably expected that any sysadmin style role knows their way around Python and the other stuff you mention, but nobody is an expert on everything. It's probably more likely that you are priced out rather than skilled out if you've done this for a while. That's not strange in itself. Experience breeds specialization, and the more specialized you are the longer you will have to look.

The answer is never to sell yourself cheap. Find out what your specialization looks like and find someone who might find it valuable.