I personally don't use these other platforms for marketing. I have heard that X is impossible to crack the algorithm, and is basically pay to win. The other 2 probably have certain other requirements.
I will say, if a "discovery site" is missing any of the following:
- A way to see new or "new and popular" posts/games/projects
- A relevant, functional search bar
- Indexing: You can find your post via search
then it is a waste of time to post and requires thousands of followers.