pressure on dusclops is far from being uselessI think the main difference between Jellicent and Corsola comes down to raw bulk and Corsola's acess to stealth rocks. If you use water absorb, then curse body can be added to that list as well, as it comes in clutch quite a bit. Here's a calc from a +1 gyarodos using bounce, assuming 130 BP from dynamaxing.
+1 252 Atk Life Orb Gyarados Bounce vs. 252 HP / 252+ Def Jellicent: 363-426 (89.8 - 105.4%) -- guaranteed OHKO after Stealth Rock and Leftovers recovery
So that's not good. After rocks are set up, the gyarodos doesn't need to predict to Ohko jellicent, and that isn't even adamant gyarados. Compare that calc to Glarian Corsola, assuming 60/100/100 bulk with ghost typing, and a +1 to emulate an eviolite boost.
+1 252 Atk Life Orb Gyarados Bounce vs. +1 252 HP / 252+ Def Corsola: 195-230 (60.1 - 70.9%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
+1 252 Atk Life Orb Gyarados Crunch(Used 130 BP) vs. +1 252 HP / 252+ Def Corsola: 260-307 (80.2 - 94.7%) -- 43.8% chance to OHKO after Stealth Rock and Leftovers recovery
Accidentally left leftovers in there, but it doesn't change the value of the calcs. So it can switch into gyarados DDing without worrying about getting ohkoed if rocks are on the field if it uses bounce, and it has a chance to live even if the gyarados uses an empowered crunch. That's a pretty staggering difference in usable physical bulks. Corsola also gets stealth rocks, and it lacks the weakness to power whip, which is much more common this gen. Another few calcs to show the difference in special bulk, assuming their both physically invested.
252 SpA Hydreigon Dark Pulse vs. 252 HP / 4 SpD Jellicent: 242-288 (59.9 - 71.2%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
Vs
252 SpA Hydreigon Dark Pulse vs. +1 252 HP / 4 SpD Corsola: 170-204 (52.4 - 62.9%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
So Corsola is also more specially bulky, and in this instance, can't die to a crit from dark pulse while jellicent can. Flinching is a definite reality here, and your only hope is that curse body activates before that happens, but that difference can come in clutch some games.
I do agree that jellicent is slept on. It is much better than it's usage likely indicates. At the same time, I think there's a sizeable sentiment that Galarian Corsola is just a fad, but I disagree. I can see the comparisons between dusclops and corsola, but corsola has a few crucial tools that dusclops lacks. Stealth rocks and strength sap make corsola less passive while having access to reliable recovery. It also has curse body compared to dusclop's frisk/pressure. Curse body is a very underrated utility that can ruin someone's day if it activates at the wrong time. For dusclops, those are useless abilities. These traits make Corsola vastly superior.
Personally, I think Corsola will be one of the walls that every team will have to contend with in their team builder, and any team that can't break it, will most likely end up being poor in the upper echelons of play.
PP stall is very much a thing and iirc dusclops gets spite and has the bulk to wear down the opponent especially w/ rest