What does the curve look like for age vs learning capacity? Obviously kids and young people are much more able to absorb information, but how steep is the drop and when does it start to seriously decline?

Im going to be 28 soon and I'm wondering if I should even bother trying to study intellectual topics at this point. I'm a high school dropout NEET, and while I've always been interested in science, math, technology, etc., I've struggled to get beyond the basics due to a lack of motivation and discipline.

Should I just give up on intellectual pursuits and accept life as a wagie?