Smash Ultimate has the issue where the deep cuts become increasingly difficult to justify as DLC because the DLC needs to be sold on top of the game. It's such a huge franchise now that chunks of the Fighters Passes needed to be iconic and popular characters.
I'd love the universe where the Howard twins, Waluigi, and Urbosa joined the fight, but we're not there just yet. Overall I think the two passes have been solid and while the game needs to go further in terms of how diverse its representation is, let's not lose sight of how impressive an accomplishment it ultimately (no pun intended) is.
Difficult to see where it goes next. Apart from with Super Smash Bros Ultimate: Definitive Edition, which adds Waluigi, Urbosa, the Howard twins, and Ultimate All-Star Mode.