Personally, I don't think the trapping abilities is the problem, it's the Pokémon that has them.
For example, would any of you be intimidated by a Arena Trap/Shadow Tag Magikarp?
This is an asinine argument--even Moody isn't broken on Magikarp. Of course nothing is broken in a vacuum, but we make assumptions about the support elements of the game has, including "an ability's user is better than Magikarp/other shitmon." A better question would be something like "is this ability broken/uncompetitive on a fairly average Pokemon?" Dugtrio and Gothitelle are both fairly average Pokemon without a trapping ability (or even below average), and both have been brought up for suspect tests in the past year or two. Hmm.
Anyway, to weigh in on the Nah/og exchange as I find it quite interesting, I think it is entirely possible that both Sableye and Dugtrio should be banned.
To follow og's reasoning here, Sab holds stall together for all the reasons it did in gen 6 (relevant to me since I have not played a game of SM competitive in any tier, so yes you should take my opinion with a gain of salt).
I am actually pretty fascinated by how stall is expected to always make safe plays because they risk ruining their defensive core with one misstep, as if an offense or balance making a zillion double switches in anticipation of those switches isn't just as risky in its own way, especially for teams with only a few ways to pressure a stall. Power creep has hurt stall, but the advent of Regenerator, Unaware, and even Scald or the Knock Off buff (admittedly useful for any style but certainly nice for crippling offensive mons as well) has also made overpowering stalls more difficult. I think pressuring a stall isn't quite as easy as og is saying if the stall player has an ounce of balls and makes some plays himself--which should be expected, just as we expect balance players who make cookie cutter plays to lose, we should expect that from unimaginative stall players, like the kind who littered the XY ladder with VenuTran/Quag/Skarm/Chans/Clef or w/e the insanely passive-even-by-stall-standards doodoo they used was.
The point here is just that something like stall + Gothitelle would almost certainly be broken even without Sableye in the tier, as it can remove anything that can pressure stall unless it's running a Shed Shell. You might point to a meta like XY and suggest it proves this isn't true, but I would argue it proves that people just didn't know what they were doing. It took awhile through ORAS for Sab/Goth stall to flourish, after all.
Dugtrio isn't in Gothitelle's universe as an obviously cancerous mon, or at least it wasn't--and I can't imagine its Attack increase making up such a difference--but many of the similarities are there, just as they have been going all the way back to Advance (where Dugtrio is my least favorite part of my favorite metagame, even if it might be a "necessary evil"). I just cannot wrap my mind around how trapping, which removes the fundamental aspect of skill from the game, is consistently defended by many players when it is so often right at the heart of these types of suspects (ie broken strategy, usually stall, is facilitated by central presence of trapping). I don't think Dugtrio has to be
the issue with stall to clearly be a part of the issue, and I find the chick-and-egg around determining
the culprit to be somewhat self-defeating when the most likely case seems to me to be that both Mega Sableye and its trapping friends are both bad for the metagame. (I haven't played SM but if Sableye is as influential as it was in ORAS I can certainly buy that is is an issue.)
To put it as concisely as I can, it is very possible/likely that both Mega Sableye is broken and trapping is unhealthy and maybe broken too, ban both if we have to. But for the purposes of this suspect, I think a Dugtrio ban can only have positive consequences--the same way a Double Team ban can only be positive. General trapping (as opposed to extreme type-specific trapping like Magnet Pull or Pursuit) is often an issue like this.
(Also, while totally outside the scope of what has been discussed so far, all forms of trapping only worsen the already-problematic issue of team matchup. I think it is bogus that, if your XY Zard-Y check was Latios, you were just shit out of luck against a mon that was already extremely difficult to check. While I get that you cannot legislate those types of things out of the game, Arena Trap and certainly Shadow Tag can be applied more broadly. Through the generations, off the top of my head, Dug + CM spam, Dug + Sun, and now Dug + stall have all been near-unstoppable
in certain matchups, and it seems pretty obvious to me that banning something that is already restrictive of the fundamental tactical exercise of skill in our game and also exacerbates matchup issues might be something we should just ban.)
