Let's call it "Joy".
I've done hard things. Many of them have a significant amount of time that is a slog. A tapestry is going to have a lot of days of just slog work. And that's fine. Doing hard things can be very rewarding. I've reupholstered a couch by taking it down to the sticks, repairing and reinforcing the frame ("hey kids, the couch isn't designed for walking and jumping on"), enhancing the design, re-springing it, redesigning the cushions so that they didn't need readjusting every time you sat down, making new foam cushions, and then sewing a upholstery. Took 3-4 months.
But, I'm in the last half of my 50s. The project you're commenting on, apt-cacher-ultra, probably would have taken 2 full time developer years to get to where it is now, and I'm doing some pretty big changes for the next version. I literally probably have a handful of that sort of project I can do left in my life, assuming I quit my job now and work full time on it.
Let me tell you, it's pretty sobering to be faced with: "I may only be doing this once, maybe twice more in my career."
So yes, building experiments where I get to try out my ideas without 2 developer-years of coding required is going to give me an opportunity for a lot of creation that I otherwise wouldn't have had. I've spent decades hand-crafting code, I fully understand the joy of doing so.