No. You get completely walled by Heatran if you run that set not to mention you power up its magma miss. At the moment, sun is a very fringe playstyle. You get destroyed by dragons and Heatran becomes a much bigger problem than it already is as mentioned earlier. In almost, if not, all scenarios, Torkoal is the better option because it has access to rocks and spin. I believe it even ahs access to yawn which makes it even more useful. Ninetales' spa is also not that great. Come on, eighty one spa isn't anything special. In the end, the only thing that Ninetales set can do is hope you catch a Garchomp switching in on you and wisp it
This is also not counting the fact that Tyranitar has also risen up in the tier as well and you'd have to contend with it and well, even a burned Tyranitar completely destroys ninetales. If that wasn't enough, you'd have to deal with rain as well and that matchup is even worse for Ninetales and finally, its alolan form is a way better mon because of hail and veil. If you really wanna use sun, stick with Torkoal. That thing has actually utility while Ninetales does not. Iirc, Torkoal also has access to body press and even though its not ideal, at least it can do something to Heatran, unlike Ninetales
Also, you're mistaken about it being broken in gen five. The reason it was broken was because of more reasons other than sun. FIrst off is sleep is just ridiculous in gen five. The sleep count resets if the victim switches out which means that if you can consistently force out a sleeping mon, it's never gonna wake up. The second reason is with Dugriito. That thing just traps and kills Tyranitar and sometimes Politoed. In fact, I even heard that there were scenarios that sun teams would use magic bouncers for the sole purpose of blocking rocks from Tyranitar, becoming sacrificial lambs in the process. The third reason is once you get rid of those two mons in the previous reason, Venusaur pretty much wins the game then and there
