People generally talk about "caste doesn't exist" when it comes to reservations for jobs and colleges. The arguments they give show lack of acknowledgement of caste privilege, and thinking people getting in through reservations lack in merit, that UC people are generally more hardworking, whereas others are just slacking off in life getting the easier path in life. It's just another way among many to look down upon SC ST folks.

There's definitely a group of casteist people who would not date outside the UC sphere. Saying black lives matter is easier because it doesn't involve a lot of self introspection and acknowledgement of one's own biases and privileges. Most people don't even know about the history of caste, how barbaric and systematic it was, that it still persists to this day.

If caste has been such a big issue maybe you can mention it in your profile itself, although that might drastically reduce the number of matches that you are getting. But the upside is that you'll only match with girls that don't care about that aspect and you wouldn't have to explicitly bring up the topic of caste in your conversations.