now before i go to actual reasoning i have to say, Personally i would love it to be banned as 4/5 of the team i like to use are 6-0d by it (granted they are rain with lando-t, nidoking+fini, spiritomb and mudsdale, and a team with raboot being the sole ice resist) so it being banned would actually benefit me, BUT if we are talking about the whole metagame, i dont think its busted.
FIRST OF ALL,
Ice typing, Kyurem hates rocks, and the main set it runs usually forgo

Boots and go with

Specs,

Lefties on sub sets and even

never melt ice (or

scarf if you are evil), because of that hazard hurts it a lot. over the times of me playing games in high ladder, if the opponent has a specs kyurem, and its usually easy to counter lead with something like

Lele,

Urshifu,

Glowking etc. and if they dont lead with kyurem, the kyurem will be hurt by hazards a lot, as at most it will come in 2-3 times in the game.
SECONDLY,
now granted those 2-3 times it will probably rack up kills but what makes it different than things like lele? We like to joke that kyurem has 0 switchins but in practice its very easy to switch into, some things that can switchin once and revenge kill it easily are

Lele,

Spdef Ferro,

Shifu,

weavile, and even

kyurem itself. its so easy to revenge kill, as it desprately needs all 3 coverage to not get hard wall, and without specs the damage isnt that big and is managable.
THIRD OF ALL,
if the kyurem isnt specs and it is dragon dance or bulky sub roost, its easier to beat imo. dragon dance kyurem is slow and so easily walled, if its offensive, it can be outsped by common scarfers like kartana and lele and get ohkoed back, plus the physical movepool is so pathetic that the only moves it can viably run are Icicle Spear, Iron Head, Outrage and Stone Edge, and things like melm and

just walls that forever, (ik theres a mixed dd set with life orb, EP and freeze dry that can threaten these, but i dont actually have much experience facing it so im going to leave it from this post and might edit it in later in the future) if its bulky with DD, it doesnt do enough damage and needs atleast 3 DD to be able to threaten something, granted it is pretty good at pp stalling heatran and pex but there are other things that can beat them both without being walled. bulky sub roost is also another good set with earth power and freeze dry that can take a lot of hits and roost it back up and drains pp from things like close combat urshifu, but this set is just hard countered by a lot like Lele, Spdef ferro and even melmetal! and the never melt ice set i agree, is pretty darn strong seeing it switch moves and able to kill things accordingly but, its still revenge killed by the same things specs do like

Lele for example.
FINALLY,
My point is,

is an excelent mon but that doesnt mean its OP, to bring up old gens, Magearna in SM is stupidly good and can do so much with so little and it is still balanced.

Kyurem in this meta i feel like has the same effect, it is a very powerful threat and with quite a few sets to choose from the nuclear :specs: Specs, the anoyying sub roost or even the rare but still excelent DD, it is entirely balanced. with threats in the meta like

Pult,

Lele,

Melm,

Glowking,

Volc,

Shifu,

Koko,

tini and

Weavile at the top of the meta game which naturally checks and kills kyurem, i dont think this beast is that broken, it is just powerful. the meta currently is very balanced and filled with Excelent mons (not broken) at the top. so i really think that kyurem should stay even tho at times it does feels anoyying to fight especially with the god awful freeze mechanic.