In the middle of watching Del's vid and I wound up pausing on the "only 6 (unique) newcomers in Ultimate was disappointing" part. This was outside the norm for Smash due to EiH, but even that aside, 6 newcomers is honestly a pretty reasonable newcomer count for any other fighting game out there. Sakurai and co have truly spoiled this fanbase.
Not that I'm complaining about Smash's consistently high newcomer count mind you, but it does feel a bit strange when you stop and try looking at it from the outside so to speak. 12+ newcomers per game (with Brawl being as high as 18!) is honestly pretty crazy. A lot of Smash is just pretty crazy and we love it for that, but it's also created a lot of ever increasing lofty expectations for what is "acceptable" for a new game.
I'd Say crossover Fighters, or just Fighters on already made I.Ps do typically have alot of Characters, and I think a Big Factor is you don't have to take time to Designing characters themselves and their backstories and Personalities, nor any Redesigns for Sequels and such.
As an example, I think it was pretty amazing that MVC3 launched with 36 Playable characters, which is less than MVC2's 56, but that game was an Asset Dump, plus MVC3 was the first 3D Game in the series.
FighterZ had 24 characters at launch, which yes did include SSB Goku and SSB Vegeta as Seperate from SSJ Goku and SSJ Vegeta, but that's still more than other Arc System works launch rosters
But I do agree that Smash is pretty crazy among other Fighting games. Smash Wii U was the First HD Game made in the series, and 3DS was the First Portable game made in the series, yet there was still 51 characters at launch, 17 of them being Newcomers.
I think beyond just the fact you are working with characters that exist already, Sakurai and others Planning the game out beforehand and not deviating too much allows stuff like this to happen.
I also think it helps that this amount of content is part of why Smash sells so well I think. Smash being the Anomly it is I think is quite a good thing, because people love Content.
That's why I disagree with the lot of you on this site that think we are getting 40-60 Characters only, and why I think we might push PAST 100 Characters on the roster. If you combine the following elements together
-The Planning that goes into Smash games
-The Namco Team that's sticking with the Series a 3rd time
-Coming off every veteran having HD Graphics (which wasn't the case with Ultimate)
-The Balance of Ultimate being the best in the series, despite having the most characters
-Nintendo allowing even more extra Development time than usual, with cases like TOTK, Mario Wonder, MP4 (being reset)
-The New Engine made inhouse by Namco that will allow more inside knowledge of how to use the engine to full efficiency, especially since it was headed by Someone that has worked on Smash for 3DS and Ultimate
-The Rumored New console just being a More powerful iteration on the Current Console
-Smash Ultimate becoming the Best Selling Fighting game
-Nintendo having probably the most money they have had ever, from the Switch, The Software, Theme Park, Movies, Mobile, etc
I just don't see a Scenario where this Next Smash is going to be a Downgrade to Ultimate, especially if Ultimate will be Backwards Compatible with this next Console. That's just the way I'm looking at things