There is a even smaller number of Sub rogues (SV 2.9% vs Sub 2.2%)
How many Hunters do you see using using Artifact skins? If want to use the forums to make judgments I could say there are you, Bepples, and Yura making all the arguments for RSV while the number of MSV are growing.
Old content becomes irrelevant as soon as the next expansion is released. Blizzard makes tweaks and changes each new release, so a level squish will make little difference on the availability of a aging expansion.
Based on your own opinions, there is nothing other than your own observations to prove the popularity of MSV. Bepples has made it clear that wow sites that show numbers do not provide enough variability to changes that effect each patch, one spec could be popular because of a raid then dropped next for one that has higher damage.
How many of those 18 use a pet?
How many can use range and melee abilities?
How many wear mail?
All these small differences can distinguish one spec from another.
If you want to say all melee class are similar enough, then using a gun/ bow over a wand makes little difference, and if you not happy with Hunters you can try one of the other 11 range specs.
Would this satisfy players? Creating a new class that introduced three new spec based on Bards, Dark Rangers, and RSV. Call it Archer then there would be another range class for players that uses range combat, but does not use pets. Bards could be healers, DR could be ranged rogues, and RSV could be called Ranger.