Good question and one I've put real thought into. Here's the full picture.
The payment situation is a mess. 'Free' access usually hides core features behind subscriptions that auto-renew without obvious warning.
Things that have genuinely helped me:
- Free trial is usually enough to judge real user quality
- Bots tend to reveal themselves in the first exchange
- Location-based platforms usually have better engagement than national ones
- Premium is sometimes worth it — but only if the free version shows real activity
Hopefully that saves you some frustration.