For the past two days, I have been dealing with issues regarding my data packs for immersive railroading. Any time I would attempt to create a world, this message would pop up.

It did not allow me to use safe mode. So, I went to my data pack folder and saw that they weren't compatible with the version of Minecraft I was using, even though it is 1.16.4. Which is the same version of the mods that I am currently using.

Here are the versions of the mods and Forge that I have to help recreate my scenario.
If you need anything else, I will send it your way ASAP to help solve this issue.
ImmersiveRailroading-1.16.4-forge-1.8.0.1
TrackAPI-1.16.4-forge-1.2.1
UniversalModCore-1.16.4-forge-1.0.0-fixed
Forge release 1.16.4-forge-35.1.4

I found a solution thanks to another issue someone else posted who was having a similar problem.