I have to disagree. For me what makes a gamemode good is uniqueness. Dark Star Singularity is so different with a new-ish map, i played it nonstop. It was fresh, fast paced and fun.
On the other side gamemodes like URF and LotPK are ok but get old imo. The reason behind that is them being too similar to the normal games. Although the same thing can't be said about ARURF since the randomness of every game keeps things interesting, nonrepetetive and inroduces different combos and plays enough to keep it interesting.
In reality there is no such thing as a perfect gamemode and we all have different opinions when it comes to deciding what's fun and what's not. Imo is the gamemode is too similar to the to the normal league (like nexus seige), why bother playing it in the 1st place?
P.S: while deffeitely not dominion isn't he best i still enjoy it alot for what it introduces like different objectives, tactics...etc. The same for Ascension.