Moltres with Sky Attack

They learned from zapdos...

Seriously.

People were upset that zapdos outclassed itself at its only job.

Moltres was already the premier fire attacker. You already got good use out of it for a very long time. Now, new moltres will have a new use, which doesn't fully overlap fire moltres. Sure, while bosses weak to both fire and flying will be better handled with sky attack, bosses weak to only fire (or fire and anything not flying) will be better handled by fire moltres. E.g. fire moltres would remain the best counter to registeel (where you so recently had good use of it), especially in sunny weather (I think only in cloudy weather did machamp match moltres).

So I wouldn't say RIP rare candy. There hasn't been new moltres raids available for ages, and research was even 5 months ago. You had many months where moltres was your premier fire attacker, and many warnings over the past few months that it would be outclassed soon...

As answered already, SA Moltres doesn't completely overtake OH Moltres. While there is overlap among grass and bug types it still has superiority over ice and steel types, which is still something worth more credit than you're giving it for. Not to mention in clear weather OH still outperforms SA except against targets like Breloom that face a double weakness to flying.

This isn't a Zapdos case where anyone with a previous investment in one got screwed. SA Moltres simply runs alongside OH Moltres, trading places depending on the matchup. The only thing that threatens to completely obsolete it is Heatran, and that's if Niantic doesn't do something like give it Ember and Fire Blast as its only fire type moves.