The actual deckbuilding of party decks in commander is interesting, as the upside of "full party" makes it worthwhile. The issue is that
Nalia and
Burakos are generally the only interesting commanders, with some people dipping into esper piles (usually
Sefris) to have access to Linvala and the Trapfinder. I have an idea bubbling about making a
Celes party-animator deck, but that's more because I want an excuse to play one of my favorite pet cards,
Exava.
I have a Burakos /
Haunted One and you get to play some really niche, unusual cards.
Bellowing Mauler and
Titan Hunter turn out to be real fucking beatings when paired with Undying and Aristocrats.
Prowling Gesistcatcher and
Body Launderer represent insane amounts of value, even if they have anti-synergy with Undying.
Vindictive Lich is hard to slot into most other decks, yet wreaks utter havoc here - and
Solemn Doomguide is brutal when paired with the myriad each-player-sacrifices creatures in the party types. Since the card types are fairly common, you always get new goodies - like
Twilight Diviner. Pair this with cards that work well with treasure generation, like
Vat of Rebirth and
Obsessive Pursuit, and you've got an engine.
The trouble is that the role that Party is playing in all of this is filtered purely through Burakos's weird interaction with Haunted One. If you swap it out to go UB with something like
Clan Crafter, the entire focus of the deck shifts. Party is only interesting in that it forces you to limit your pool and play cards that you might otherwise overlook, with the payoffs outside of Coveted Prize being on the weaker side. In the end, this design space is better served by having individual commanders care about it, like
Vaan,
Voja, or
Maralen.
Outlaw just shows how shallow trying to code super-tribes as a 'mechanic' is, as a card like
Double Down is just getting slotted into rogue, assassin, or pirate deck - there's zero reason to try to try to make it fit elsewhere, and absolutely no incentive to try to feature several of the types.