Are non-legendary Fire-types that worthless?
Not a single one makes the Attackers Tier List (Houndoom is listed with double-dark moveset) or even honorable mentions. That was when Exeggutor and Venusaur were raid bosses. Are they that worthless in the current metagame?
RIP my Arcanine/Charizard/Flareons who took down many Exeggutors and DG Blisseys under the old gym system.
Answers
I don't think that they are worthless, it's just that there are so many of them without one really distinguishing enough to be separated out. I have a 100% fire fang/fire blast Arcanine that I maxed out to level 36.5 that performs very well and rates high on pokebattler for raids but he will never be listed as a top counter or attacker because too many options exist of the same type that are just as good or better.
They aren't useless, it's just that the legendaries have the ability to be better. However being better is largely a moot point, since basically all fire pokemon are useless in the current meta (based on the dearth of grass pokemon used by players most of the time). I personally haven't bothered to power up any moltres of entei yet since there is no need, my flareon, arcanine and charizard (which are all already powered up) do just fine in the few situations I need to use them.