Basically the "updates page" loads in a non rich html format, and if theres an update it's missing the tabs on the update page as well. I can't figure out if this is just because apple may have stopped supporting El Capitan or if I have something else going on. Any help would be appreciated. I've trashed the caches in library and the user profile. But this page is the only one that still loads like this (see pic below) on my app store.
It's been that way for quite a while - I'd assume it's simply no longer supported for El Cap, but I have no citation for that.
You have to bear in mind that there will no longer be any updates for any apps on El Capitan [nor indeed for the OS itself] - many apps are now minimum spec Mojave, some a little older some newer, but no-one is going to be testing against El Capitan any more. It was superseded 5 years ago & generally support is to 3 years.
As noted, this applies up to High Sierra - the only difference on High Sierra is it lists all the updates you can't have, also in plain text ;)