I'm going to be entirely honest: I don't see any merit in trying to ban Wishport Clefable.
Without a doubt, Clefable is not only the best Pokemon in the current metagame, but also harbors one of the best sets in Wish + Protect + Teleport + Moonblast. We know how incredible this set is, not only in its defensive utility, but in the fact it can heal worn down defensive behemoths that can't heal reliably for free. What makes it so good is that, unlike Xatu/Gardevoir/Gallade, it doesn't need to compromise its team slot, as it is able to do much more than pass Wishes such as check Dragon spam, and its godlike utility as a whole goes without saying. Consequentially, I've noticed a lot of people are mentioning how they think Clefable is the problem, as it is utterly overcentralizing balance. While I believe that this is an issue, I don't believe this in of itself is Clefable's fault. As the Melmetal suspect passed through, I made many observations regarding the role that Clefable played in balance, and I realized that Clefable itself isn't the problem, but rather offense itself.
There have been many relevant arguments regarding how much Dracovish constrains teambuilding in its own right, alongside behemoths such as Kyurem and Zeraora. Despite how we have lost Z-Moves and Megas going into Gen 8, we also lost a lot of defense in turn as well, and we gained a lot of unprecedented wallbreakers. Whether they're completely new or simply refurbished with new moves, it is without question that these Pokemon are a problem at their core. I addressed in
this post here in more detail on how Clefable more or less was trying to act as a team captain trying to keep defensive Pokemon healthy to keep taking on these offensive threats. With this in mind, it's unsurprising that Wishport Clefable is so good in a meta where Pokemon can dismantle defensive threats that struggle to keep themselves healthy, especially with AT now gone.
However, I don't believe this is a case of broken checking broken, as I feel Kyurem and Zeraora offensively are only as powerful as they are because of the meta that they're surrounded by. Even if Teleport is the issue, I feel the true culprit of it and Offense's strength (and currently the bigger issue regardless of if Teleport is broken or not) is
Dracovish.
Truthfully, there have been a lot of arguments regarding suspecting Dracovish, and at this point, I can't help but agree. The defensive metagame loses so many of its options just to not lose to Dracovish that options to checking things like Kyurem and Zeraora are severely limited, and allow for them to freely dismantle the metagame without much of an issue. Seismitoad, for instance, is used so much because it compresses a Rocker, Electric immunity, a generally defensive Pokemon, and, most notably,
a water immunity. Gen 8 marks the first time possibly ever where having a Water immunity is a huge reason as to why a Pokemon is viable. As of this post, Seismitoad sits at the
A rank in the Viability rankings, and despite the time since the last update, I feel this hasn't even remotely faltered. Despite 3 straight generations of mediocrity, suddenly, it's an OU staple, mainly because it checks Dracovish. As a result of the overbearing strength of Dracovish, ultimately mediocre things like Seismitoad are run, and in turn, further encourage use of Wishport Clefable so it can do its job while making sure Dracovish and co. doesn't utterly dismantle its team.
As a result, Dracovish puts such a strain on defense because you have to always consider that chance of running into Dracovish. If you don't have Ferro, Pex, or an Immunity, you lose at team preview--even then, Ferrothorn and Pex are still greatly dented by Fishious Rend, especially in the Rain. Dracovish fits every bill of overcentralizing that is suspect-worthy, most notably,
warping the metagame around itself. Water immunities and resistances are required almost exclusively because of Dracovish, and the defensive metagame is forced to lose out on options just because Dracovish will dismantle it otherwise. Wishport Clefable has to be used, because it is the only real way that things handling the offense of the metagame can really do their jobs.
theotherguytm did an amazing job explaining as to why Dracovish is a problem in his post earlier in this thread, which you can see
here.
Overall, it's true that Clefable is overcentralizing how balance is to be played, but I can't help but say that the source of the problem isn't Clefable itself, but, rather, the reason as to why it's so centralizing to begin with: offense. More specifically, the issue is Dracovish forcing options away from relevancy that could legitimately check Zera/Kyu/Terrakion. Thanks for coming to my Ted Talk