Im not sure why exactly but Mekanism Addons is the one that cause the problem. I have my own modpack and im trying to make another one. i i had the same exact problem but only with the new modpack. I was looking the mod list on my first modpack and i saw that Mekanism Addons is not even there so i removed it from the new modpack and the game load correctly now. I think its a new mod cuz i love mekanism and installed everything about that mod in my first modpack and i never saw the Addon before. Maybe just wait for an update before adding it.
