Back at San Diego Comic Con 2024, it was confirmed that Cartoon Network vs. Jellystone!: Crisis on Infinite Mirths would be released on this year's fall, but it didn't happened, so here's my theory on why it hasn't been released yet:

On the Hanna Barbera Wiki, it says that every episode of Season 3 of Jellystone! (with the exception of Meet the Jetsons) were all produced in 2023 before being released in 2024. It says that Crisis on Infinite Mirths was produced here in 2024 itself, so this makes me think that the special will be released next year (2025) after being produced here in 2024 itself.

And there you go, my theory on why Crisis on Infinite Mirths is yet to be released.