Make it more fun & less serious (while still keeping the challenge intact). Esports need casual viewership to thrive, & the MDI misses that almost entirely, while also missing out large portions of the core playerbase. Some ideas would be...
Add threats that can bounce between contenders.
Add random mobs/bosses from other dungeons in place of the expected ones, so each run isn't exactly the same.
Red shell Mario style?
It needs to do something zany to attract attention, because at the moment, if you've seen one run of a particular dungeon, you've likely seen them all. The MDI players/presenters may say the money involved isn't worth the time required, but that's only because the viewership isn't really there, so it's either time to mix it up & go with something that mixes up each game entirely to make it a much more entertaining spectacle, or just let it wither away & die with nothing but it's dedicated audience.
I'm certainly not going to watch the MDI because Mage was banned for one run.