FLIF has been integrated has the lossless mode of JPEG XL, the next JPEG standard.
FLIF was superseded by FUIF and then by JPEG XL, but it hasn't been fully integrated. JPEG XL has parallel decode and uses MAANS entropy encoding instead of MANIAC, which results is slightly less compression for some situations (but faster decode). That said, I certainly agree that JPEG XL is already very impressive and hopefully the next majorly supported image format.