I can't download the patch. I have over 23gb of free space on my PS4 but it tells me "To download the content, you must delete unnecessary content from system storage." I won't be deleting anything. What is the problem?
Welcome to the ESO patch system! Do a search here, this has been discussed ad nauseum in the past.
Basically, ZOS uses large repository files that have no provision for being updated partially.
If one byte changes inside a 400MB repository, they are re-downloading the whole 400MB file.
PS: As a result, even small patches are usually in the GB download range.