>>28224356Yeah, it's because:
1. its ability can't support the rest of your team (unless you stack Flying-types, and that usually would be dumb). Note how most of the teams that use Bronzong also use Kyogre. Kyogre's rain + Levitate means it's IMMUNE to PGroudon, which is huge. It means you force a switch.
2. its strongest attack is single-target, whereas PGroudon and PKyogre's strongest attacks hit both opposing pokemon with only slightly less BP and an acceptable amount of risk of missing. It also has the drawback of lowering Ray's defences, so whatever partner pokemon Dragon Ascent did not KO can KO Rayquaza back.
3. it's weak to Xerneas.
4. it's weak to Intimidate.
5. you lose out on running other, (possibly better) mega pokemon.