Isn't EQ omnipresent in VGC?
Other than Ground-types like Landorus, Earthquake isn't really too omnipresent in VGC as more special attackers dominate here. Rock-types prefer going Rock Slide if they can learn it.
Landorus-T is easily the most common VGC Pokemon, and it's so common that it alone would make Earthquake omnipresent. Heatran is also common and has Earth Power which can't be blocked by Wide Guard.
Interestingly, some damage calcs of Lando-T vs Stakataka: (inputting it's stats into Bastiodon)
252+ Atk Landorus-Therian Superpower vs. 252 HP / 0 Def Bastiodon: 172-204 (102.3 - 121.4%) -- guaranteed OHKO
252+ Atk Landorus-Therian Earthquake vs. 252 HP / 0 Def Bastiodon: 160-192 (95.2 - 114.2%) -- 81.3% chance to OHKO - note damage is reduced in Doubles because of spread
Having a shot at surviving a x4 STAB EQ is no joke. But more importantly, Intimidate is omnipresent in VGC. With Intimidate support, it will always survive said attacks.
If you want to survive EQ without Intimidate, Relaxed 252 HP / 20 Def lowers the chance of a OHKO from Earthquake to 6.3%. Strangely it needs 132 Def EVs to guarantee the 2HKO.
It seems like a pretty reliable Trick Room user with some support. Something like Togekiss to redirect special attacks and Fighting-type attacks, whilst Stakataka itself can survive the Earthquakes that can't be redirected with proper investment. Then once it's set up, it can abuse it's super strong Gyro Ball.
Helping Hand can also be very good support for it. Cresselia can use TR for it as Pyritie mentioned and Helping Hand. Of note, it means Lando-T is a risky switch-in.
-1 252+ Atk Iron Plate Bastiodon Helping Hand Gyro Ball (150 BP) vs. 4 HP / 4 Def Landorus-Therian: 184-217 (111.5 - 131.5%) -- guaranteed OHKO
Or with an Relaxed 252 HP / 236 Atk / 20 Def set:
-1 236 Atk Iron Plate Bastiodon Helping Hand Gyro Ball (150 BP) vs. 4 HP / 4 Def Landorus-Therian: 165-195 (100 - 118.1%) -- guaranteed OHKO
The latter means that Lando-T can actually come in after Lando-T knocks out something (avoiding Intimidate), survive the Earthquake, and OHKO with Gyro Ball.
I think Stakataka has potential in VGC if it has the right support.