Gliscor has nothing to do with this. It could be in the tier and it would still be a high skill based metagame unless it got voted to get banned. The core reasons for SS OU being seen this way include it having no generational gimmick with Dynamax banned, as well as Hidden Power being removed. Unexpected coverage is a lot harder to pull off in that tier and it's a lot easier to formulate gameplans because at most it's guessing what items the opponent has unrevealed. Gliscor would be very strong in a world with no hidden power ice and no tera blast ice, forcing urshifu/slowbro/weavile to do their best to keep it in check, but it would not be able to tera itself out of a 4x weakness like it does in gen 9. It would also lack Spikes and probably lacks Roost, meaning that it would most likely want to run some combination of Swords Dance + Knock Off + EQ/Facade to threaten Corviknight/Clefable, but no EQ comes at the cost of being walled by Melmetal + Heatran, the latter of which you would probably want Gliscor to act as a counter for.
The lack of gimmick alongside heavy duty boots being used on regenerator mons makes SS OU boring, but it rewards those that play consistently well over the duration of each game. You have to carefully plan out turns because it's easy to lose progress off of regenerator letting torn/slowbro/pex go from early KO'd to back to full, or easy to play passively and have the opponent set up a Future Sight + Teleport combo into you being forced to lose a mon.
Personally I call it the "no nonsense" tier and like it for that reason, and more people are liking SS OU for that reason after experiencing the chaos Gen 9 brought. This post was a bit off topic and theorymons a bit, but I wanted to reply to that.
was one of the main forces discouraging Zap-King-Lu type structures, at least not directly. These structures tended to fit 
or 
as win cons, which can switch into dd/mixed kyurem at least once and force it out, which may alone be enough given Lu's hazards. Further, 
was a solid enough scout/pivot into special kyurem. especially with the adaptation of psychic noise for subtect. Its relation to Zap-King-Lu is more relevant when discussed in the context of Kyurem's role in preserving Gliscor. But for now, I don't think the viability of these structures will be too affected until/unless future tiering action occurs.
is almost certainly the main winner of this ban, but I think it's important to look past the type chart when discussing its relationship with Kyurem. First, Kyurem was not a Gliscor counter, and could not really come in without being crippled, as every Gliscor runs either Knock or Toxic nowadays. Gliscor's whole shtick is lasting the entire game, so a short term check doesn't really prevent Gliscor from executing its gameplan, at least in a vacuum. And it has also been discussed to death that Kyurem is not the only viable ice beamer, with options like 
and 
being arguably even more splashable and viable in the first place. However, what Kyurem did do was:
(speed control, spinner) and at least retest 
. Regardless of how you feel about the Volc ban, I think we can all agree that Volc's defensive profile is greatly missed, even with Kyurem banned. Volcarona:
, 
, 
(specifically wisp + draco over wisp + darts), 
(lottery simulator), and special spam in general
as perhaps the final tiering action of this gen.
