So the new decks will have some old cards
The use case is still (say it with me now!) Bruvac the Grandiloquent, but Lo and Li, Royal Advisors created a Petitioner commander with an aggressive angle
Meanwhile, Song-Mad Treachery is a card I really like for a reason similar to Pelakka Predation: people don't expect non-sacrifice decks to have Threaten effects, which means that Song-Mad Treachery can lead to some massive blowouts by stealing an unsuspecting opponent's best creature and smashing them with it
Teferi, Who Slows the Sunset is a four mana white and blue planeswalker who enters the battlefield with four loyalty
or even Halana and Alena, Partners that all dole out additional buffs of their own
(Although I should note that we do push these decks to fringe levels every once in a blue moon.) Utility discard cards, on the other hand, do not necessarily promote the discard decks unto themselves (although they are used if enough resources for the discard deck exists)