I don't think you need to stick to just one style, like classic rock necessarily. What really matters is listening to singers who articulate well - and that exists in pretty much every genre. The thing is, a lot of people listen passively, letting the music play while doing something else, and nothing new gets in. That doesn't work well for pronunciation.
Try this: pick a song you actually like (even if it's pop), and spend a few weeks with just that one. Listen to it multiple times, then try singing along, even if it sounds bad at first. The idea is to get your mouth used to English sounds - how the 'r' works, how the person breathes between words, the contractions that show up in actual speech. Also look up the lyrics online (sites like Genius have them) and follow word by word while you listen, especially in the choruses. That's where you really pick up how the sounds link together.
Another cool thing is picking artists with lighter accents if you're just starting out - mainstream Americans tend to be clearer than fast-talking British people or artists with very strong accents. But honestly, one song you like that you repeat is worth more than ten podcasts you find boring. Consistency is everything, and if you're happy listening, you'll stay on track.