I loved running Linux in college and tried every new (or old) distribution and compiled oh so much stuff and fiddled with every new (or old) thing I could find to fiddle with and thought it was super cool to write config files by hand and be able to read and modify all the source to everything I was running. As you point out, this was an excellent learning experience for me.

I kept doing that for awhile after I graduated, but eventually I realized it wasn't a good learning experience anymore, it was just a tedious waste of my time. I realized I should have been socializing or recreating outdoors or reading or picking up new hobbies if I wasn't working. Since then I've mostly used Macs or Linux machines maintained by the company I work for, and this is definitely a much better use of my time.

There are only so many fundamentals to learn here before it becomes just so much minutia and non-essential complexity.