You send a thoughtful message, hoping for engaging conversation. They respond with "lol" or "that's cool." It's frustrating, but what does it mean?
Sometimes they're just bad texters. Sometimes they're not that interested. You can usually tell by whether their responses pick up the conversation or just kill it.
What to Do
If you like them, suggest a phone call or in-person meetup. Some people just communicate better verbally. If they're consistently giving minimal effort, move on.