As per a dev request on the Discord channel, I'm reposting my issue here to make it easier on the devs to track/address my issue.
I'm on a Mac, and no matter what steps I take, I can't make any mods appear/function in TCE. Even the mods that come pre-loaded that are meant to be possible to activate out of the box (TRex, etc) don't appear on the mod menu/function in-game, so I think this is unintended behavior/a bug rather than an issue with bad mods.
The mods I subscribed to from the workshop didn't get downloaded to my mod folder. (The pre-loaded mods ARE in there, but don't appear on the in-game mod menu, nor do they appear to function.) I tried downloading the workshop mods manually, unzipped them, and put them in the folder with the pre-loaded mods; nothing. Then I tried going to the User/Library/Application Support/Steam/SteamApps/workshop/content folder, where I found the workshop files(which were, aside from the file names, identical to what I'd manually downloaded from the workshop), unzipped those, and moved them to the mod folder. Still nothing.
As far as I can tell, I'm doing everything right, but the game is not recognizing any mods - including the mods put in the correct folder by the devs themselves. On the Discord channel, BlackCobra009 mentioned there was a bug where some users couldn't get mods to show up until they deleted the mod zip-file in C:\Users\<username>\AppData\Roaming\Maschinen-Mensch, which apparently fixes the issue for those users...but Macs don't have that file path. If there's a similar stopgap measure for Mac users until a patch addresses this, I'd love to hear it.