> isn’t airline maintenance one of the most documented and standard procedure focused of them all

I hope you're right :) You probably are too. But even with that, there is a reason it's a profession and not something we ask gig-workers to do, it takes expertise and skill like any other skilled work, even though all the literal actions one might take is technically written down somewhere. Even in such industries, experts would get "hunches" about what is wrong, and are able to quicker pinpoint issues, and similar things. Or "getting a bad feeling" before something is actually evidentially bad, which prevented human disaster more than once in history.

I think if you consider that the job couldn't be done by just anybody who can read and follow instructions, then it might not be as easy as just "follow what the manuals say" and in those cases expertise, knowledge and experience matters a great deal.