I believe I've encountered that guys electrical work, and it ain't sage :)
(I.e. there are a few of those "fix it all" guys, but they're not always code compliant. They do get stuff done, though)
Most other things (besides obvious big things like foundation, drainage, roofing, load supporting areas) can be done with a good "fix it all" kinda person, or (with patience) youtube.
I only call the plumber when I don't have the equipment I'd need, like cameras and snakes.
The thing I won't do is roof work. Too scary.
And that's why you're still allowed to DIY it.
If schlepping packs of shingles onto a 150deg roof was as easy as pulling wire or laying pipe (heh) they'd have trade groups and lobbyists convincing the government to keep you from doing it yourself just like the lower altitude trades do.
I had a boss who was up on his roof installing an antenna when he slipped and fell off. It was a scene from a 1920s comedy -- his wife was looking out the window and saw her husband's falling body flash by.
Only it's not funny IRL. His liver was punctured, he lost his spleen, and his back was never right again.