There's more to writing than clarity, though. Not all written communication needs to abide of the efficient/clear writing style of technical documentation FFS
But there's not much more important, stylistically, to writing an business email or document than clarity. It's absolutely the most important thing. Especially in customer communications.
In the UK there is/used to be a yearly awards scheme for businesses that reject complexity in communucations for clarity:
But anyway, you don't have to act on all the suggestions, do you? It's completely different from the idea of getting an AI to write generic, college-application-letter-from-a-CS-geek prose from your notes.
With enough repetitive suggestions asking for the same thing, it will just continuously push your writing style towards this ultra-dry writing. Plus, even in business emails it's important to show a human side in writing.
It's not like Grammarly's push for clear writing actually helps in any way. Most times it just outright suggests removing relevant info from the sentence. They just push for this service as a way to incentivise subscriptions, writing quality be damned.