Back to game from before 2.1

Any way I could find a comprehensive guide/list to catch me up on everything I have missed?

Welcome back! Here are the patch notes for all the patches from 2.1 to the most recent (2.35):

Patch notes for the two main content patches (patch 2.2 ~ Through the Maelstrom and patch 2.3 ~ Defenders of Eorzea):

2.2 patch notes
2.3 patch notes

Additionally there were several smaller patches done in the months between those main patches which also added new content, equipment and the like, so these are the patch notes for them:

2.15 patch notes
2.16 patch notes
2.21 patch notes
2.25 patch notes
2.28 patch notes
2.35 patch notes

Hopefully, this has helped! :D

Also 2.1 patch notes.

Reddit's "What Have I Missed" page is nice, too. (It's under Useful Information at the top of the main ffxiv reddit page, which also has other handy links.)