Been lurking here for a bit but finally decided to post about this.
I've noticed a huge difference between platforms that moderate actively and those that don't. The ones that don't tend to become unusable within a few months.
The free tiers on most of what I've tried are basically useless. You get just enough to see that real people are there, then hit a wall the second you try to actually message anyone.
Feel free to share whatever has worked for you, even if it's not the obvious answer.