World doesn't load

Any of the following could have caused this problem:

You have a taxing thing happening every tick
You have a block generating at a far to high rate
You have mobs spawning at too high of a rate
Or your device cannot handle something else in the mod

if the problem does not resolve after you have checked all of these then I would check for a windows update and
then uninstall and reinstall mcreator. (If you uninstall, make sure that you have your mods saved as mcreator-runnable files)

If the problem STILL persists then tell me!

I hope I have been of assistance!