Yes it is.... If you like using your brain. Like many things, it's actually pretty easy, once you've put some knowledge inside the noggin.
We must have a different definition of the word fun then. 
Guess so.
I've only had to track down electrical gremlins a few times in my short lifetime, but with my primary profession of being a computer programmer, I deal with tracking down minute problems in complex systems on a daily basis.
Did similar things only in the circuit world for years. Minutia is not a stranger to circuit design or repair. But, I happen to like the physical realization of accomplishment and having something in my hands that is tangible in the physical world. I happen to like solving problems were the outcome is a device that you can clearly see, feel, or touch, and functions as intended. And, being successful at it, is enormous fun. And, figuring out why is an adventure in itself. Having said that, the fun is gone if there are time pressures involved, either impressed upon or self imposed.
There's no part of your profession that is fun? No wonder mental gymnastics seems abhorrent. I can see that if you hate your job, learning electrical basics won't be fun either. Searching through or creating lines of code wasn't something I enjoyed, either, after I learned the basics. I made sure people didn't get the idea I was good at it, so I wouldn't be asked to do it.
Sure it may be pretty easy to do with the right knowledge, but it takes time and a decent amount of guess and check. I guess I just don't find that particularly fun.
Guess and check? No wonder you hate it! A few minutes of basics and the right, very simple tools and you don't HAVE to guess. Electrical behavior is very much in the physical world realm and predictable.
Personal attitude make a great deal of difference on what is fun. Few people like to do anything they feel forced to do. Certainly, if you'd rather do something else, the current task whatever it is, is distasteful. Many of the members here like to work on their bikes. Electrical is just another aspect. And, it is far simpler with these bikes then modern ones. I also found being an electrical hobbiest, and building various circuits fun, too. Getting paid to do it, certainly didn't hurt skill expansion.
I suppose we have different goals regarding these old bikes. I rather like working on them and making all aspects function properly, as well, as riding them, and admiring them... for fun. It's a hobby for me. Aren't hobbies a waste of time and a bit of mental exercise?
Cheers,
