The lag while typing makes it unusable. Also inclusive language is not grammar.

Add-on ignores its settings and runs on sites that are marked as disabled. If you want privacy you have to completely disable it.

Free account is very limited. 500 word count limit.

Politcally charged grammer fixes.
ProWritingAid lists the term "biological sex" as problamatic as it could "offend transgenders".

Please keep your grammer tool politically neutral.