You could make the same argument that "Using Open-Source Code Will Make You a Bad Programmer" -- and in fact, a generation ago, many people did.
These things are all tradeoffs. A junior engineer who goes to the manual every time is something I encourage, but if they go exclusively to only the manual every time they are going to be slower and produce code more disjoint and harder to maintain than their peers who have taken advantage of other people's insights into the things the manuals don't say.
I'm trying to think of any examples of someone who said that "a generation ago" at all? I assume that they were some sort of fringe crackpot.
I think for software engineering, the far more common issue is that there's already a best practice and the individual engineer hasn't chanced to hear about it yet than the problem on the desk is in need of a brand-new mousetrap.