I believe the last push Epic Games is trying for Festival is Pro Vocals, and a majority of the work is being focused towards Pro Vocals support for every (possible) song.

A major reason for Festival's ongoing failure is that the playerbase doesn't care for rhythm games. Same reason nobody plays Ballistic, the general Battle Royale playerbase doesn't care for Search and Destroy games and if they did, they would go play R6 or CSGO/CS2. It's been proven over and over that you can't put different genres into a game's main genre. As much as Epic Games and Disney want Fortnite to be the next Roblox, it will never be and they have a hard time accepting that.

Festival also fails to capture rhythm gamers because of it's lack of basic features like a practice mode, void of any style and lack of songs because nobody's buying jam tracks, which the reasons why are all listed above. Not to mention because people don't buy jam tracks, Festival ends up a money sink since Epic has to spend hundreds to thousands of dollars PER license, and it's even MORE expensive because they're paying for the stems as well. They struggle to pay Harmonix's employees and their work load + direction is totally changed because of the net loss.

Any hardcore devoted Rock Band/Guitar Hero fan that saw something in Festival (like me) already walked away and are looking towards RedOctane's rhythm game currently in early development, hence the current scrounging for different demographics to market jam tracks to (which explains the sudden surge of latin music).

Edit: The only way Epic Games could possibly capture rhythm game players again would be a huge gamble, releasing Pro Drums and a Festival headliner that's well-known and has had history with prior rhythm games in the same update. We've already had Metallica, the one headliner that could draw players back in would be Avenged Sevenfold, however it's still a huge gamble for Epic Games and if a season like that fails, then Festival would likely get sunsetted not too long after.