From personal experience Tandem really depends on who you end up talking to, at its core it's just a chat app. Italki and Preply are more for finding an actual teacher.

The problem I also face is crippling social anxiety. I can manage with keyboard/messages okay, but when it comes to voice I'm for whatever reason absolutely terrified. So for instance if I did end up finding someone to talk to in Japanese or etc, I'd have to get to know them first through keyboard before I feel comfortable enough verbally talking to them. It's also always to do with calls. I'm fine for text and meetups, but calls/video calls. I'm very hesitant.
Absolutely daft, I know. But it's a hangup I have.

This also all being said, I do think the best course forward for me for now, at least vocalising plan wise, is to meet up with some people on some social services online like Discord or etc, maybe completely unrelated to languages, then maybe migrating to Discord Call or VRChat.

I do appreciate the suggestions, I just don't know how well I'd take to it with the fear and all. Also, always a joy to see your messages on here, but my instance keeps blocking your replies on the post so this is about the only time I can properly respond to you too, but just wanted to say that.