I see Grammarly as helpful for people whose English is their second language. I don't use it, mostly because I am an English teacher, and my husband acts as a back-up proofreader.

As an editor here on Medium, I ask people to use the audio feature and listen closely to what they have written. Assuming they are good speakers of the language, the gaps in their writing should stand out, and if there are connections missing, that too should be evident.

Also, they should read their work aloud also. Personally re-reading your work is one of the best ways of developing as a writer.