Our brains all generate relatively the same amount of happy/sad chemicals, so it turns out the satisfaction of winning a nobel peace prize and the satisfaction this person feels fixing their dumpster dived keyboard can only be so different in magnitude.
It's not like doing universally meaningful things unlocks some kind of super-happiness, so there's no reason to shy away from "unmeaningful" things if they bring you joy.
Whether this represents a good or bad use of one's time, who can say. Some things, people do because they enjoy them, even if the activity doesn't make complete economic sense.
I'll never go back to membrane keyboards.
I have a rosewill that is made from cherry brown switches and apparently the minimum electronics to make it work reliably unlike the low end one OP wound up with. Probably cost me $80 six years ago but it works the same as it was new, and I expect to get a decade out of it no problem.