The thing is, it's happening for so many mods, it causes the game to fill the log with those for a full minute or two. It's so long, it over half a megabyte of error, pastebin wouldn't let me add all of it, I had to use Paste.ee
This is also another error I seem to get a lot of:
[14:52:06] [Client thread/ERROR]: MultiModel minecraft:builtin/missing is empty (no base model or parts were provided/resolved)
Removal of Optifine cuts down boot time but the errors still occur.
It doesn't crash, in fact, most of the messages are warnings, but there's still a bunch of errors. The game doesn't crash, but with Optifine the game takes a few minutes longer to get through the errors. Log Here