Mortal Kombat 1 is adding an entirely new mode to the mix with Invasions. According to Mortal Kombat co-creator and NetherRealm Studios Chief Creative Officer Ed Boon, it's essentially "a greatest hits of [Mortal Kombat's] single-player experiences."
From my own personal experience with the new mode earlier this month at an event hosted by the developer, that's more or less an accurate summation. Mortal Kombat 1's Invasions mode is effectively the culmination of every minigame, unlock system, and tertiary game mode ever introduced in the franchise to date. It's a narrative catchall that combines all of the above into a bloody version of Super Smash Bros. Ultimate's World of Light, providing a light, gore-coated RPG dusting to what is typically considered more of a standard fighting game.
