People have conversations to connect with others and gain comradery. Responding with a blanket "I don't like this" statement cuts off the conversation and can make the person feel like they are being belittled or ostracized. Basically its like you are taking the conversation and throwing it in the trash.
It's not just about your opinion, it's about the other person's opinion AS WELL. The goal of a conversation is not to just be direct, it's about gaining perspective and understanding.
For example, I fucking HATE country music. I've grown up in an area where 99% of the radio stations are country music. My entire life has been me trying to avoid hearing country music as it is EVERYWHERE around me. If someone starts a conversation with me about country the music, the first thing I want to say is I HATE IT! But, I've learned to avoid doing that. Instead I ask them what is about country music they like or how long have they been a fan of it or who their favorite artists are. Something that is in line with the conversation they are having so they feel that I am engaged and connecting with them. After that, then I tell them that I fucking HATE country music and provide a few details as to why I hate it. But I always ensure I am not belittling them or their opinion when I do that, I just share my personal experience and reinforce that I am happy they enjoy country music as much a they do.
It's not just about sharing your negative opinion on the matter, it's about understanding the other person's position or feelings on the matter. You can share your negative opinion, you just need to ensure you acknowledge the other person's opinion as well.
I will say that your explanation of the same 100 classic rock songs being the reason you hate it is 100% accurate and I totally agree with you. It is an excellent point and easy to prove. So sharing that opinion isn't a bad thing at all. But it's really easy to derail a conversation if your response is just a negative without having engaged with the person first. Try engaging with them first so they feel like you've listened to their point and then gently bring your opinion into the conversation.