Honestly, its a simple "slayer" concept that they should've implemented awhile ago.
One reason I keep playing smite is not because of conquest, but because of arena where its a 5v5 blood bath which adds constant gameplay. League lacks this form of gamemode and blood moon finally gave it to us, but even better since even in smite there is some CSing for points whereas in blood moon there's a couple objectives but not enough to take away the excitement from the game.
I'm just glad they limited the champion pool cause it just shows how much more fair, enjoyable, and even ironically diverse the game is, since everything actually has to fight and the enjoyment out of playing as or against tanks, adcs, or supports is severely hindered. Sure assassins are broken but they're equality broken which makes everything in the gamemode kinda balanced (rengar is still bullshit tho) and fun to face.
Additionally the leveling system shows how much more enjoyable league is when a gamemode doesn't feel extremely one sided off a few kills or gold lead.