I tend to view this in it's historical context.
Before about 20 years ago skis were long skinny things with a nominal sidecut of about 50 meters and only the most skilled skiers could actually carve a turn and the large turn radius meant that they were going really fast when they did. The other 99% of skiers happily skidded their turns.
Sometime in the mid-90s shorter 'shaped' skis with nominal turning radii of under 20 meters replaced the old "straight" skis, and it became possible for ordinary people like me to carve. Carving became the new "thing" and there was a school of thought that said carve everything all the time and never skid.
The thing is, while carving railroad tracks is a lot of fun, few of us can actually do it in any conditions other than a sparsely populated blue-square groomer. Steeps, trees, bumps, crud, etc require a modification of the pure carve, a smeared, slarved turn becomes necessary. Of course, to be effective, these kinds of turns are based on the pure carve rather than just twisting your skis sideways and hoping for the best.
So, I think the bias against skidding is aimed at those who never got beyond the skid-twist technique that most people used on the old skis. If you're not tipping the skis and engaging your edges it's going to be darned hard to progress beyond groomers. Carving is a lot of fun and worth pursuing for its own sake, but what really makes it important in terms of overall skier development is that in order to carve you need to get the skis up on edge and develop edge-awareness, and once you're able to crank a turn with zero slippage you will have the necessary edge-control to slip sideways a bit in a controlled manner with you deciding who much to skid, not the mountain.
Which is to say, that a good skier carves when he or she wants to and effortly skids in a controlled manner when appropriate. Nothing at all wrong with that. For myself, I like to carve and I'm perfectly happy to ski mostly on sparsely populated blue-square groomers to do it. YMMV.