Learning to interact socially with NTs is important, I agree. It takes a lot of practice and concerted effort, and a key to leaning to enter conversations and engage in group settings, in my experience, is to understand the role that nonverbal cues play in NT social interactions. We tend to not only be unaware of nonverbal cues in others, but we also don't tend to produce these same cues ourselves in the same ways that NTs do.
And I think this also gets to your original question of WHY people don't seem to enjoy talking with you. I know I shared this same frustration for many, many years, and it was only after I began to understand the role of nonverbal cues (eye contact, facial expressions, body language, etc) that I began to understand why other people reacted so differently to me than they did to others. Just coming to this realization can be a huge relief, in a way - so that you understand that you are not crazy and the universe isn't conspiring against you
The thing is, NTs are, for the most part, unaware of how much they rely on nonverbal communication. They just sense something is "off" or, worse yet, they subconsciously interpret your behavior as being rude, disinterested, etc. So try not to take it personally when NTs don't always react the same way towards you as they do towards others - they've quite possibly just misinterpreted your nonverbal cues without even realizing they have done so.
While it's not likely we are ever going to fully master the art of nonverbal communication, we definitely can improve our skill set, and just being aware of the problem can be an important first step in learning to socialize.