Geez I have quite a lot to say about this Pokemon.
Talonflame is a fast Pokemon that can outspeed heck of a lot of other Pokemon, but...
Yeah, Talonflame was only my favorite Pokemon in Gen 6.
In Gen 6, Talonflame had access to the amazing ability Gale Wings, which gave priority to all Flying-type moves and let me tell you I loved Talonflame because of that. But in Gen 7 and 8, Gale Wings was nerfed so bad that Flying-type moves were only priority moves when Talonflame had full HP. Even damage from overworld weather without having Leftovers to heal the damage back up could make Talonflame have a useless ability.
Which is most of the reason why you don't see it in Gen 7 or 8 battles. And if you like the ability Flame Body, then Volcarona or many other Pokemon are better Flame-Body-users then Talonflame
But in Gen 6 OU I use it quite a lot. That said, I only ever had 5 or 6 Gen 6 OU battles...
But all of my battles, or at least majority of them, I used Talonflame and it was fricking OHKO-ing some of my opponent's Pokemon, because in Gen 6, Talonflame had Gale Wings and I used Brave Bird over and over again.
That all said, out of all of the Gen 6 OU battles that I have seen, barely any of them had Talonflame as one of the members. So just how viable is Talonflame in Gen 6 OU?