Sabella vs Mael in SPL Week 5 (this week) shows something that I haven't seen discussion of: Eject Button.
http://replay.pokemonshowdown.com/smogtours-gen7ou-250673
Mael used Eject Button Amoonguss to eat a hit from Greninja and then trap it with Dugtrio. This was seen last gen on Wonder Trio Stall with Eject Button Seismitoad. The key difference is that everyone playing against Wonder Trio Stall should know that's coming, but Sabella had no clue and it couldn't have been scouted for.
This begs the question: Can Dugtrio always be dealt with through counterplay? I think it can mostly, but it seems clear that Eject Button into Dugtrio is very hard to deal with and players can't exactly prep for it. It comes out of nowhere and beats their wincon, and since it can't be prepped for it therefore takes skill out of the game.
Also Destiny Device's game shows how Duggy Pursuit-traps A-Marowak, which otherwise would have plowed through everything.
http://replay.pokemonshowdown.com/smogtours-gen7ou-250787
So when
GH[O]ST claims that Duggy doesn't bring anything absurd to stall, I'd argue it does; it invalidates breakers that are otherwise extremely viable and even gives stall a way to beat Alolan Marowak, which otherwise 6-0's stall. There are indeed multiple stall builds, and Dugtrio is a necessity on each and every one. Even when a Mega-Sableye -less stall team was built and found success, Dugtrio was still there. So much for the often-claimed requirement of Sab on stall; when there's a trapper, there's a way. Duggy doesn't even need Arena Trap for some mons, and that is very telling of how difficult it is to deal with.
Personally I think if Duggy goes then Pursuit-trapping stall (see Banded Weavile) will take its place, and that opens up a new can of worms. Regardless, I think Dugtrio is more toxic than any other trapper in OU.