At least for me, I think half the value in building to learn was that the knowledge and skills acquired in the process, especially cursory skills and knowledge, might be useful in the future, even if there was no obvious path to application at the time.
I built several projects at home, many involving learning e.g. graphics programming and rendering, that would never be useful in my professional work, but which were intrinsically interesting and enabled me to build other, more useful projects later on. It also gave me greater confidence in my abilities as an engineer, and cursory skills I learned in the process did help in my professional work.
Now it feels like what’s the point. The machines can or will be able to build anything I could want, useful or not, faster and with less frustration. I probably won’t be able to be employed as an engineer long enough to build a career on said skills. And I can’t mentally justify not spending that time with friends and family, when the expected return is basically zero.
I still find math, science, and engineering interesting and intrinsically rewarding, but in a closer sense to how one might feel about playing video games. The information is or will eventually be useless, so it isn’t worth spending a significant amount of time on.