I dislike it because it just swings the aram problem from one end of the spectrum to the other.
The problem it attempts to solve with range being too powerful, it just swings the opposite way - with mark/dash, engage is too powerful.
Suddenly, any champion that is great in melee but just has trouble gap closing is oppressive. Meanwhile, champions that were great before got even better, such as Katarina and Talon.
It has simply changed the aram from "I hope we get poke" to "I hope we get Malphite/Gnar/Jarvan/Katarina/Talon/Alistar/etc". The worst part is the change mostly benefited tanks who wanted to engage. So now it's a game full of tanky people who can get on you easily, so that despite building tanky they still do damage - and it is just SO BORING.
"Oh look, the 4 tanky bruisers just dashed in. Guess our 5 squishies will just die while they try to whittle down their health..."
It would be ok if this wasn't aram and you could pick champions to counter tanks...but it's not. It's ARAM. At least before those without engage had the option to buy things to shore up that weakness like Randuin's, Talisman of Ascension or Righteous Glory. But now, what do squishies have to buy to counter the tank steamroll?
Not a thing. That's a much worse problem IMO than what mark/dash was trying to solve in the first place.