Duolingo is very much on the Enshittification path, seems like they fired a number of translators and have the rest just proofreading AI.
For the interested, here’s the place where you can request your personal data and delete your account
Duolingo does have grammar lessons, they cover the parts of speech, rules, exceptions and interesting notes.
You actually have to click the grammar notes for each lesson, and many people skip it. Still it’s up the user, not sure why this myth persists.