If you haven't made any config changes, delete your config folder.
Don't rely on a speedy response around here, we're all doing this in our free time and sometimes we're off helping other people, sometimes through other mediums
A lot of the Docs are outdated, it is recommended to not make your recipes and loot tables manually, but to use datagenerators.
Take a look at how Forge makes its tags and how Minecraft makes its recipes
I don't think JustEnoughResources is updated to 1.15 yet.
Please check out StopModReposts.
Additionally to my knowledge Optifine doesn't have a version compatible with Forge 1.15.2 yet, you can check this by checking the changelog for whatever Optifine version you have.