I would debate this specific example. Tapu Bulu's inferiority stems from lacking Grassy Glide, Knock Off, and U-Turn as very significant moves on Rillaboom, but the Fairy typing adds very significant resistances to Bug (U-Turn common to neutralize), Fighting, and Dark regardless of the Dragon Immunity's relevance (neither takes Poison well and Steel offense is not a common tool). This goes back to my point that the additional Fairy typing is not what makes Tapu Bulu an inferior choice: if you shored up other flaws I pointed out like Grassy Glide priority, Knock Off to push progress, or even a unique "missing" thing in not having a Fairy STAB, Tapu Bulu would easily be competing with or overtaking Rillaboom, especially because it lets it punish Grass's Dragon concern. You also can't brush off the Dragon STAB because most don't run one "other than Meteor or busted Signatures" when I dare you to name a Special Dragon that DOESN'T want a 140 BP move to nuke things mostly-neutral; for Signatures, okay they're signatures. Still very strong Dragon moves you have to be able to survive getting hit by. Does Flying not deserve discussion as a strong attack type because its most reliable moves are Recoil Brave Bird, Hurricane, and Signatures like Dragon Ascent?
If you're going to talk min-maxed users, Salamence and Garchomp pop out for pre-Fairy Dragons, and after it there's Dragapult, Archaludon, Roaring Moon, and the Beast Paradoxes. You cannot point to Fairy having min-maxed users to downplay the value of the type itself over Dragon. Fairies that claim at most goes to Legendaries-and-alik like Xerneas, Zacian, Tapu Lele (and part of that is Psychic Terrain for its other STAB), Iron Valiant, and Flutter Mane (for whom half the burden is on its Ghost typing as well offensively and, in VGC, Defensively).