A huge problem with Grammarly, made worse by this, is that it becomes the equivalent of Académie Française for English and no further development of the language is permitted. If it's ingesting current writing and all new writing is put through its (not it's - I had to delete an apostrophe there which drives me mad) mill, there can be no progress.
AI is destined to make our lives so dull it will hardly be worth living.