Yet here I am as a self-taught hobby mechanic who has built a touring bike from scratch with a used frame. It works just fine despite mixing components that are not supposed to be mixed. Nobody ever taught me how to wrench, it was a matter of reading (and watching) stuff on-line and acquiring specific tools over the years whenever I needed them.

I would not feel confident wrenching on other people's bikes for money, but I will do anything (including lacing wheels) on my own bikes and for my friends and family. I have nothing against professional mechanics, but seeing how hard it is right now to find a shop that will even take your repair job if you haven't purchased your bike with them, I'm so glad I acquired a decent skillset over the years and am independent in that regard.

Now if you'll excuse me, I'll be downstairs for another DIY attempt at bar tape that is going to be a disappointment.