no argument that playing ranged takes less skill, i agree there.
leblanc is ranged.
zed can mark, if it hits place his w behind his team, dash, q,e, w back behind his team and be back in under 100 ms, and take 10% of your health + the damage the spells do thanks to his passive. 100 ms is you average east coast ping so you know, he will be back before you even see that he is there. When their mark dash combos are faster than you ping its not a skill issue, its a game health issue. (similar combo with leblanc) there are many many more examples here of champs that can go all in and not even use their mobility to engage the way they are intended to.
meanwhile against VI you can cancel her ult entirely every time she tries because mark dash makes you untargetable. so VI doesn't even get an ult in aram anymore. other high impact abilities suffer the same fate oriana, nami, and naut ults come to mind
realistically mark dash gives some champions unhealthy trade combos and takes a great deal away from champions that didn't have a lot in aram to begin with.
It sounds like you would want this added to SR too, but that's my beef with it. i want to practice teamfighting, but when the teamfights are so dramatically different due to added mobility on everyone they aren't comparable to teamfights on SR.