I used to think "yes", based on what I've seen a lot of "CNC only" people do. Where I do my machining, there is a Tormach machine that people are able to use if they take a brief class on it. Since there is a manual mill next to it, sometimes they will do a quick cut on that instead. I once had a person lean over and ask me "Don't you think this end mill is cutting poorly?" and I said "yes, if you spin the bit backwards." Other times, I see people just using totally the wrong speeds and feeds for what they are cutting. Lots of folks these days jump straight to buying or making or using CNC machines as a project or coz it's cool, but don't seem to really know what is going on.
As a brief personal history, I've done a few years worth of manual milling, but it was never with an eye towards doing it properly. It was always some ancillary task for some larger project, and the only reason I would mill was because I needed bracket A to fit slot B, or because the professional machine shop had too long of a lead time. I never thought about rpm=cs x 4 / d, or anything else and went thru end mills pretty quickly. (I wasn't paying for them.)
When I left that environment and now started having to pay for my own end mills, suddenly I started caring a lot more.
Now I haven't done CNC yet (plan to soon), but all of the "proper" machining practices I've learned recently seem to be CNC related, like climb vs falling cut, feed rate, importance of no backlash, etc.
I would have thought that somebody who had proper CNC training were taught these things from the start, as they are fundamental to expeditious metal removal. And they don't worry about stuff like backlash, so of course climb cutting makes sense.
Sometimes I feel like manual machining is like driving an old stick shift car, where you manually have to adjust the timing, or playing around with the stupid XF86config files (for your linux dorks). It's kind of like, sure you get a better "feel" for what is going on, but who cares, it doesn't work as well as the modern equivalent. And some things are better left to the dustbin of history.
I'm just a young punk (in terms of machining), so maybe some older and wiser folks have a better perspective.