Cutting down on characters wouldn't have necessarily sped all the other sections of the development up.
The way video game development works is they staff people for different segments of the game and usually in the final stages they're polishing stuff. It's almost certain the character artists and animators, and any engineering resources (and xml scripters) were entirely different staffers than the rest of the team. The only staff they'd have had in common was QA, and cutting out a few characters would have saved them days, not months.
Despite Sakurai saying this game was not a port from the Wii U version, it seems to me as though much of the groundwork was taken from that game. Thus, a large part of the development time was indeed creating characters and balancing them. I get your point, and for many games what you're saying is probably true, but I don't think so for Smash. I don't think they can pump out a new character every single day as your post implies.
And on a side note, it looks like my suggestion for getting a dark version of TinyMCE to match the dark theme seems to have been implemented. Thanks to whomever made that happen! :)