dual subtitles are actually doing more work than you think, but you're right to be skeptical about the grammar part. here's the thing - if you're following 60% of what's happening, your brain is picking up patterns in real time, matching sounds to words, and seeing how sentences flow. that's solid foundational stuff. the problem is you're probably leaning too hard on the english subtitle as a crutch, which lets your brain skip the spanish processing. try flipping it: spanish audio with spanish subtitles only for a few episodes. yeah, it'll feel harder at first, but you'll actually force yourself to parse what you're hearing instead of just recognizing cognates and guessing from context.
grammar absorption from netflix is legit limited though. you'll pick up colloquial patterns and common phrases - 'qué pasa' conjugations, subjunctive moods in dialogue - but you won't systematically learn verb tenses or why you use 'por' instead of 'para'. most people who actually get fluent through shows combine them with something structured on the side, even just 15 minutes of focused grammar a few times a week. think of the show as reinforcement, not the main course.
the "feeling productive" trap is real with language learning. after 3 months, if 60% comprehension is where you're landing, you're moving at a reasonable pace. keep the netflix habit - it keeps the language in your ear and it's way less painful than flashcards. just patch the grammar gaps with something targeted, and swap to spanish-only subs so you're actually engaged with the language instead of reading the english translation.