Ahh, that one.
The website (https://www.loudnesspenalty.com/) works a lot better than the plugin, FWIW. It runs in the browser (no upload), is free, and actually calculates integrated LUFS rather than guessing at it based on real-time measurements.
For informational purposes and to help put its results in context, it's probably worth analyzing some songs from some recent releases that you like to see how much they're turned down. The fact that your song is being turned down is not necessarily always a bad thing.
I'm a fan of Ian Shepherd, both as a person and as an engineer (if nothing else, my room started being inspired by his home studio), but that site/plugin has caused a LOT more panic and confusion about levels than he ever intended. I can't think of their titles, but he's spoken about it several times on youtube (his channel: https://www.youtube.com/@ProductionAdvice).
