It’s not like learning stops but the curve flattens out a lot. Another problem is that in tech 20 year old knowledge is worth way less than 20 year old knowledge in for example cabinet making.
This is a widely held position, which sort of makes it a self-fulfilling prophecy. But I'd argue that it's not true. Most of what I know now that is really valuable isn't related to the technology of today or 1986. It's related to how to work, how to design systems, how to decompose problems, how to scale, etc. etc.