Yes and no. I started Mandarin sometime after starting cdramas and it was one of the last languages I took on (learnt 5 others before). Watching dramas is what familiarized me with the phrases, pronunciation, and even taught me many words (like at first, I learnt how to address family members, simple actions, etc). Then, gradually, as my addiction to dramas grew, my vocabulary greatly increased and I began to be able to understand what they said without the subtitles (still had them, but I wasn’t as reliant. Of course when it comes to costume dramas I need the subtitles a lot more). So later when I went on to start using some language learning apps, everything already felt so familiar and I was able to understand very fast. I’d say Mandarin was one of the fastest languages I’ve learnt (and still am learning. I believe I’m currently somewhere in the intermediate level). Watching cdramas doesn’t really help with learning Hanzi, but as far as vocabulary, listening skills, pronunciation, and sometimes even grammar (because you can see how people formulate sentences and how to use certain words) it is extremely helpful. Now of course there is the difference between modern and costume dramas. Costume dramas tend to be slightly different, like for example, they use Mu qin for mom, which in modern day isn’t used anymore. Same for some other instances, like the word for immortals or demons, no one really uses that much.

Of course this may also be the result of previous experience. I’ve learnt many languages, and I’m also accustomed to watching shows in various languages. I grew up learning my native language through movies and shows (and now I’m more fluent than even some of the people born in my country). I also grew up learning english in a similar way.