Aram is considered a fun mode that is the reason why balance it different from the other mode because aram is inherently broken, that is why it has a gap close summoner spell , amazing Invisability detection and more items to defend against poke.
How is ARAM inherently broken or any more of a "fun mode" than any other permanent game mode? I've never been able to get an answer to that besides "ARAM is uncompetitive because it just is."
By the way, your facts are a little off. Mark/Dash was a (misguided) attempt to help out melee champs against poke comps. Furthermore, the vision item options are exactly the same as on the Crystal Scar (and TT before the mini-rework). It's also far from amazing, since Sweeper is lackluster, and the removal of Twin Shadows means there is no AP vision item. Finally, there's literally one item (Orb of Winter) that's ARAM-specific.