My issue with Grammarly has always been that many non-native English speakers rely on it to ‘correct’ their English without realising that it only finds about 40% * of their errors and sometimes ‘corrects’ things that are fine. Whereas native speakers might have enough language knowledge to make their own judgement about some of Grammarly’s inaccurate suggestions, non-native speakers may blindly accept them.

* Visit my profile to find the article about the investigation I did which gave me this statistic.