>>56502906>Aside from Heatran, fire type aren't great defensivelyThere are plenty of good defensive Fire types. Moltres is currently higher tier than Zapdos because it's a really great answer to offensive threats like Zamazenta and Kingambit. Let's not forget the stranglehold that Incelroar has on VGC either.
That Fire types aren't good defensively has nothing to do with Fire itself but Game Freak not making bulky Fire types in the first place. You can't say a type is good or bad just because of the Pokemon within it. If Game Freak made a type that was SE on everything and resisted everything but only gave it to Sunkern, the type would still be horrifically busted.