[scrapheap]

First of all - things change, you aren't the person you were in the past (this isn't a good or bad thing, it's just what happens).

Some things will decline, but what declines in one person will differ to another.

Some things will improve, importantly your knowledge base will improve (a good knowledge base is an older coder's superpower).

Before comparing your problem solving abilities with your past-self have a look at what your past-self was doing. I suspect that when you look back at it you'll find that the problems they were solving were simpler problems, had a narrower scope or ran in more stable environment.