I didn't do a lot of what you would consider home brew. Mostly kits, but they seldom stayed perfectly stock either. Built a Heath DX-35 for my novice transmitter. At the time, novices were limited to crystal controlled oscillators. You changed frequencies by changing crystals. I hated trying to dig up the correct crystal, so I built a crystal switch for it. Seemed pretty simple, but the long lead lengths affected the frequencies, and on the early design kept them from oscillating at all. Lots of fiddling for a 13 year old.
Later, I built transmitters, accessories, and a Benton Harbor Lunchbox for 6M. Kits came from Heath, Allied and Lafayette. That Lunchbox at the end had almost no original parts left. Converted it to PTT. Then I hated the super regen receiver element, so I did a superhet conversion I read about in 73 magazine. Upped the power a bit (to 50 W) with a tube substitution and rebuilding the output stage. Then I wasn't happy with the stability or the need for crystals, so I designed and built a VFO and radically went with transistors.
I credit a lot of that to why I went into engineering, although it probably is the other way around. My son doesn't have those same opportunities in electronics, but he is still tinkering with stuff and is a senior getting ready to enter college, naturally in engineering. I think the drive is bred into us, the skills come from fiddling.