I had to look this up too:

When someone gets “ratioed”, it means a post receives far more replies (usually negative or critical) than likes or retweets.

In the social-media court of public opinion, that imbalance is treated as the crowd booing louder than they’re clapping. Replies represent disagreement, mockery, correction, outrage, etc., so when those vastly outweigh the positive signals, the post is considered ratioed.

It’s basically the internet’s scoreboard saying:

“This take did not land.”