Someone made a morph mod for FORGE in 1.16.5, and it's actually pretty good, you get the mobs abilities and it's essentially 1.16.5 port of the metamorph mod, however it's extremely new,
Identity Mod (1.20.1, 1.19.2) - Mobs Morphing - 9Minecraft.Net
Morph Mod (1.16.5) | Minecraft Mods
Morph | SpigotMC - High Performance Minecraft
Morph Mod - Attack Of the B-Team Wiki
Morph Mod (1.16.5, 1.12.2) - Morph Into Any Mob - 9Minecraft.Net