A simple question deserves a simple answer. No, CAD/CAM does not diminish quality. I too started on the drafting table and was good at it. But I jumped on the opportunity to be on e of the first to use CAD and explored 3D CAD immediately with outstanding results. The interesting issue around quality was that back in those days, engineering required that my CAD models meet the 2D drawings "exactly" and of course the 3D CAD modeling found flaw after flaw after flaw in the design. That of course lead to me being the pain that nobody wanted to talk too. I'll lay odds that some of these guys are still around today and remember. I have also contacted some of these guys over the years and almost all will say that they must have been out of their mind to think that 2D Ink on Mylar was more accurate then 3D CAD modeling for design. You see, when I left, the company felt the unfortunate pain of a single expert leaving. CAD use became a requirement for everyone.
Ah yes Checkers. Well, again some functioned extremely well but the work overload and ability to properly do any sort of accurate tolerance analysis was pretty much non-existant. Howerver, where checkers became doomed is when they "took advantage" of the CAD technology and started sending drawings back for totally non-valued changes that had absolutely nothing to do with quality. They became editors who wanted entire views moved around, endless dimensions positioned slightly different, font changes, text size changes, underline this and don't underline that. So I think it fair that some responsability for the unfortunate doom of checkers be accepted by many (NOT ALL) checkers.
I do however think there is great opportunity for checkers to return to be what I think they really ought to be and that is in dimensional management being specialist in the dimensional management control or tolerance analysis. Stuff that has real value. My guess on the elevator example is that the dimensional control was non-existant or just plain in accurate and again nothing to do with the CAD technology.
I will say this; Original thinking, Innovation, still takes just as long. CAD does not help that, which is often misunderstood. Use of CAD speeds up the development of an idea, but the talent and time it takes to originate the idea is still worth it's weight in gold.