Tried to make the best possible set for each mon so far. Slowbro and Glowking are the two suggestions I have for Regenerator pivots if you want either of them.
Your team actually isn't terrible, only slight modifications to make each member's best set given the team. You don't really
have to change anything, these are just suggestions.
Pory-Z is a gimmick pick just as a Pokémon so I didn't bother it. It's ok, actually a pretty good stallbreaker but I don't think we've gotten someone sadistic enough to make a stall team yet.
Meow is a pretty good set, regular spikes are better than toxic spikes though and Hone Claws is kinda pointless if your actual nuke is Leaf Storm (Special move). I don't hate Hone Claws as a choice, but give it Flower Trick and Triple Axel if you're gonna use it.
Excadrill was kinda fine, but this set is slightly better. Iron Head and tera Blast are equal in value, but only if you save tera for it which based on Pory-Z's set you will not. But EQ is kinda non-negotiable cuz it's insanely strong, SD is excellent, and Rapid Spin is very useful, so your last slot will be your brick break/Tera Blast/Iron Head slot.
Mienshao. Fake out, then base your next move off of what you think will happen. Pivot out with U-Turn, hit a psychic or ghost switchin with Knock Off, or nuke someone dumb enough to stay in on a weakness with High Jump Kick. Missing would suck, but you have regenerator.
Pivots. Don't feel like you have to use one, but they work really well with Mienshao and Future sight can force switces into Pokémon that your other Pokémon can handle. Chilly Reception is a really good switching move because it activates Snow, stopping Sun, Rain, or Sand teams in their tracks. Slowbro also works, albeit slightly less so.
You could also do that and just put Pokémon from past teams together. That's what my new Legue team is. Granted, two of them came from my regular competitive team but it's a solid enough concept.