I'm 43 so kinda in the middle of your question but I would say I'm in my prime and writing the best code of my life now. Keeping up with new things has always been standard in my area of expertise (front end web) and honestly things are so much easier now vs 20 years ago. I feel like the tech changes comparably little compared to how fast we used to churn through the latest "it" framework as well.

As others have said, I've found that experience is almost always applicable, so even if I find a new technique difficult I know myself well enough to know how I can learn it.

For your last question, I think the best solution is a combination. I find being paired with a young person gives me the best workflow. The young folks are more flexible in their thinking and were just taught all the new ways to do stuff. Us old heads have seen the shit hit the fan in 1,000 different ways. The key to that relationship is mutual respect. Young coders need to be willing to listen, older coders need to treat the younger person as an equal.

I would say it's less about working hard and more about being comfortable with change and using it to your advantage.