Datapacks stopped the world from loading
What it looks like in your log
Failed to load datapacks, can't proceed with server load. You may need to remove them or fix them.
What causes it
A datapack, or the datapack a worldgen mod injected, references things that no longer exist. This usually follows removing worldgen mods from an existing world.
How to fix it
Restore the removed mods, delete the broken pack from world/datapacks, or start once with --safeMode and accept vanilla settings.
Not sure this is your problem? Paste your log and Roastd will tell you which of these it actually matched, and what else it found.
Check your own log