DeepL is different in my opinion. They always focused on machine learning for languages.

They must have acquired fantastic data for their Models. Especially because of the business language and professional translations which they focus on.

They keep your intended message in tact and just refine it. Like a book post editing. Grammarly and other tools force you to sound like they think is best.

DeepL shows, in my opinion, how much more useful a model trained for specific uses is.