Only the skier with superb innate athleticism can ski anything very well. The rest of us need skis that are "right" for us.
As skis in any model line are made longer they are also made stiffer. That certainly complicates any review or demo. For example, my 170 cm carvers and 188 cm powder skis are each just right for me. By the way, both are one size below the max offered in each line (Head SuperShapes and Dynastar Mythic Riders). Some ski model lines are made to "ski short" and some are made to "ski long."
While there are probably no bad skis, there certainly are skis that are difficult to ski in certain circumstances or unsuited to certain skiers with their particular skiing style, strength, speed, technique, etc.
I have no idea why some skis feel right to me. My 170 cm Head iSuperShapes wood core with sandwich construction and my 170 cm Head Xenon Xi 7.0 cap construction skis feel very similar and I like both a lot (the Supershapes have more pop on rebound and grip ice better; the Xenons have a bigger sweet spot and carve clean or skid very easily). The Xenons were under $350 pro price with bindings and are my usual every day skis except in deep snow or very hard pack. I don't care what the construction of the ski is...sandwich or cap, wood or no wood, I just care what feels good on my feet.
I really like Peter Keelty's www.realskiers.com/ $20 subscription site ski reviews where he rates skis for different skiing styles (carving or skidding), bumps, powder, etc., and seems to have the best reviews I've seen. I've done well using Peter's reviews to make up a demo list, and even to pick the skis I'll buy and end up liking a lot.
It may be that some of the polarization of different skis relates to that ski model's ability to be less versatile...well suited to certain conditions or skier styles and less well suited to other conditions or styles. Other ski models are more versatile and get either ho-hum reviews for skis that are decent for almost anything but not great for anything, or for skis that are great just about everywhere.