Spin on torkoal is just moreso "Idk what else to put on here, this looks good", so sun teams have to use something else like hatterene, or play at a truly breathtaking, neckbreaking pace, due to torkoal's weakness to hazards. Another thing is that the physical defense is good, but with no recovery it is really hard to abuse it.Torkoal isn’t as bad as you say. It gets both spin and rocks. It is physically impervious and the tech is to actually use its stronger attacks and try Body Press. Torkoal actually 1v1s Tyranitar which is comical. It beats Kingambit unless Gambit is 5 fallen. It’s good into Iron Valiant as well. With Tera, you can use Torkoal to check pretty much any physical threat you need it to.
For sun-specific pivots, they do exist. For slow pivots there is Landorus-T, Corviknight, Mandibuzz, Raging Bolt, and Slither Wing. For fast pivots, there is Landorus-T, Roaring Moon, Cinderace, and Slither Wing.
0 Atk Gliscor Earthquake vs. 248 HP / 248+ Def Torkoal: 116-140 (33.8 - 40.8%) -- guaranteed 3HKO
Even something like gliscor has super effective coverage against it. In a tier with so many grounds, being weak to them you have to either be able to ko them before the can hit you, or have another trait that overwrites the weakness. Body press is a cool tech, so I am interested in that. It's decent into valiant, though most have knock off which torkoal is very fearful of.
While tera does help torkoal check things, you're using your tera on torkoal... I don't think that's a good use of tera, since so many other sun mons benefit much more from tera'ing, being forced to use it on torkoal is unideal. It would morseo be a last ditch effort.
The main issue with torkoal is that it is hazards weak and it has no reliable recovery, which means it can't be the tank it wants to be. Pelipper simply having roost and being immune to spikes is massive, since it means it can come in more often. Torkoal can come in maybe 3-5 times a game, which may be enough sometimes, but long term is not going to work.