Watching films with Italian subtitles makes sense, but it really depends on how you do it. If you're just reading the subtitles and completely ignoring the English audio, then yeah, you're probably wasting your time because your brain will take the easiest shortcut. But if you read the subtitles while actively listening to the English, trying to connect the words you hear with what you're reading, it becomes a useful exercise especially for your ear and vocabulary. The real magic happens when you start recognizing entire sentences without looking at the subtitles, and that only happens if you use them as support, not as a lifeline.
To make it more effective, you should gradually switch to English subtitles, not Italian. I know, it's harder, but that's where real learning happens. At first try watching films you already know or ones with simple, clear dialogue: like animated films, light comedies, or basically content where people speak in a relatively natural way but not too fast and not full of slang. Avoid high-tension films or thrillers where the dialogue is all whispered or overlapping.
What really works is combining this method with other things. Try watching the same scene twice: first with subtitles to get the general meaning, second without to really hear how the words sound. And if you find a scene with a phrase you don't understand, stop, reread it, then try to repeat what you hear out loud. A bit boring? Yeah, but that's how you build language muscle memory.