Gary, I totally understand the mentality that results in the scenario you describe.
And, aside from noting how inefficient it is in the "replace part; try again" scenario (although, to be real, in some cases, "replace part; try again" is absolutely the correct approach), I think it's important for us to understand that this approach will not work in the future when everybody is working in a multi-discipline environment.
The "replace part; try again" scenario has always been an option of last resort. If we think back to the type of hardware diagnostics we did in the 1980s, a lot of that was the only approach that worked. Pull all of the expansion cards. Reboot. Plug 'em back in one at a time, and see what happens. Same approach applies to software/services. Disable all the services. Turn 'em back on one at a time, figure out which service is causing the problem. These are all DIAGNOSTIC tools!
But even those tools seem to have been lost, from a logical perspective, in what I'm seeing today.
You are absolutely correct in that "critical thinking skills" are NOT developed on-the-job. Those are skills that are developed from classroom education and exercises designed to develop those skills.
Where I'll disagree, though, is that it does NOT take a "genius" to possess and use critical thinking skills. I truly believe that 90% of the people competent enough to work in IT in the first place, have all of the mental capabilties necessary to develop critical thinking skills; they just need a motivated mentor to help them do that.