Honestly, as long as their is ANY pure rng anywhere in it it is unfit for being a ranked mode.
Psuedo rng of some given form can be fine, but pure rng invalidates any competitive aspect.
Store uses pure rng? Game can't be ranked.
Minions/monsters use pure rng to determine if they drop an item? Game can't be ranked.
Glacial has a pure rng % chance to proc? Game can't be ranked.
Gunslingers have a pure rng % chance to do their thing? Game can't be ranked.
Etc. Etc. Etc. Etc.
Of course, this also means that regular LoL is unfit to be a ranked game because of crit chance, but I can forgive that due to the option to not build it at all or build it to 100%. Regardless of my forgiveness it does need to be reworked to not use pure rng.
At any rate back to TFT there is just way too much pure rng all over it to even think about forgiving any of it, so Riot should not even consider ranking it in any way.