About 4-5 years ago I started making a new class, and I'd like to get feedback on it from people outside my friend group (one of the players in my game is doing a sort of test run of it). but there's nowhere on here to post completely new classes, is there anywhere that I'm not aware of that I could post this to get some feedback?

I believe you can put it in a Google Doc or other sharing service and post a link in the homebrew section asking for advice.

Ditto, there's actually a few forum members who sort of have this workshopping group for new classes, or adapting older edition classes to 5e.  I don't know how much actually play testing of each others work is done, but you may want to look for them in the Homebrew forum I think "New Classes" is the subject.

I thought they announced the ability to make custom classes as being a priority for them a while back, but I don't see it on the current roadmap. I keep checking back periodically but keep being disappointed - I really have no interest in subscribing without the ability to do so.