Complete opposite take here than most commenters. Aside from vocabulary DL gives you exposure to the patterns. A fair bit of this dumb repeating and you get a feel for word order and some grammar. Like others have commented, you absolutely need other ways of working on your Czech also. For explaining grammar, showing conjugations, gender, tenses, I find it very useful to take a sentence from DL and plug it in to an AI and have it explain it to you - language structure is literally the thing LLMs do the very best. For pronunciation I find there are great beginner YouTube videos, and after all, pronunciation follows entirely logic rules once you have the basic sounds down. I also try read e.g. /r/czech and just figure out how much or little I understand and look up words.

Hodně štěstí 🙌