Cradily said:
So continuing on from here:

- Cradily doesn't get much benefit from switching into scald for sp.atk boost as anything can't already beat will easily outspeed and kill it, and anything it can already beat it... already beats, and is unlikely to work more than once or twice in a match.

- Stall teams don't exactly fear the attack drop from scald, as they are not attackers and likely have ways to deal with it (Aromatherapy, etc).

- Cradily has to rely on your opponent not having common coverage moves in Fighting/Ice, with Steel (which resists all your attacks and immune to Toxic) likely rising up the ranks due to the new influx of fairies (and poison). Otherwise Cradily just loses if they're not weak to Giga Drain, and Grass isn't exactly a great attacking type.

- Cradily has to rely on the opponent not having set-up sweepers. Common Dragon Dance users resist Giga Drain (Gyarados has Ice Fang and if it flinches or freezes during the Recovery spam it's done), Calm Mind/Quiver Dance makes Giga Drain essentially useless, and Swords Dance outboosts Stockpile.

- Cradily's low speed allows Encore, Taunt and Trick users easily being able to shut it down (with Haze ruining Cradily's day as well).

You can certainly make Cradily work, but I feel there's too many threats that are able to shut it down for it to be 'viable' outside of it having a niche in a sandstorm team. But by this logic Kabutops/Omastar could be viable in their niche of rain teams, but was excluded from your list of viable fossilmon.
Sorry for the late Reply

Being Honest i Forgot about Kabutops Omastar Niche on Rain teams,Also thats why it is NU because it is too passive,and there are any threats able of shutting it down,is not that bad but i said it was viable because i used one on a sand team and made it work, but now that i think about it i had an entire team to cover its weakness so i may have been biased.

Just a saying but Cradily has the problems that most stall mons have plus that typing that dont give it a lot of room to swich into.

Talking about other Topic Zard Y and Kyu-B got pushed down to UU and then were quickbanned.