I honestly think
Shuckle should be looked at. Aside from the sets that may be considered gimmicks (even though they can be extremely powerful in some match ups) like Contrary SSmash/Rest/Infestation/Toxic, the sets that I really wanna bring attention to are the Sticky Web ones. Why? Because, in my opinion, one of the things that usually keeps Sticky Web in check is the fact that most setters are, simply put, bad. They are either too weak, too slow or too frail, so they usually get one or two shots at setting them up and that's it (fun fact: Shuckle has the highest BST out of all the mons that learn Sticky Web).
So, that's where Shuckle comes in: making great use of basically any HP stat ever, Shuckle can easily become one of the hardest to kill mons in this meta and given his movepool, one of the greatest pivots. Shuckle's movepool is not all that diverse, but it has just what it needs. Sticky Web + Stealth Rock means that whenever it switches in, it can keep momentum by setting either one. Toxic means non poison/steel defoggers can't switch in freely if they're also needed to take care of other threats (more on this later), Encore makes sure Shuckle is not used as setup bait and Knock Off is always useful for getting rid of leftovers and potentially choice items.
What really makes me feel like Shuckle is too much sometimes is how it can deal with real, big threats in the meta (252+ Atk (150) Life Orb Smeargle V-create vs. 252 HP (120) / 168+ Def Shuckle: 114-135 (28.1 - 33.3% ) / 252 SpA (150) Choice Specs Swellow Boomburst vs. 252 HP (120) / 88 SpD Shuckle: 87-102 (19.5 - 22.9%), for example), while harassing defensive mons with Toxic and potentially Knock Off, and putting pressure on you to defog the webs away, not only meaning that if your defogger is needed to deal with something else, it's gonna have this extra pressure over it, but also that you're always being forced defog (as defoggers are way more common than spinners) any rocks you might've set up, which in turn makes Shuckle's life much easier, as SR is probably Shuckle's only real weakness. Also, Shuckle's effectiveness and longevity means offensive teams lacking consistent hazard removal and not using Sticky Web are already at a huge disadvantage
Now, I don't need anyone telling me how you can deal with Shuckle. Yes, I know you can Taunt Shuckle or that Diancie-M exists. My point is most teams don't have a Magic Bounce mon and even if they have a Taunt mon, are you gonna double switch every time you have a mon on the field that can let Shuckle in? My argument is based around how much Shuckle can do for a team.
I think Shuckle's best set is probably something like Leftovers/ Iapapa Berry, any ability honestly (it's not stuck with Sturdy given how it's p much never getting OHKOed) and Sticky Web-Stealth Rock-Toxic-Encore/Rest/Knock Off.
tl;dr: Due to Shuckle's absurd bulk, decent typing and access to two amazing hazards, including Sticky Web, a hazard that has no good setter in normal play, it can act as a pivot during the match, taking hits that most offensive teams wouldn't be able to deal with otherwise and almost never having dead turns, as it can always set one of its two hazards or cripple something with a Toxic or Knock Off. This works so well because simply having Sticky Web up is really game changing, something that's not true for most other hazards (atleast not to the same extent). It also pressures defoggers, which can either help its teammates or Shuckle itself, by keeping rocks off the field.