Don't take anything personally.
Everybody moves at a different speed, and if the speed isn't working for you, take it as a sign. I have found that people who take their sweet time responding end up being a little selfish, because they don't see you as a person who's investing time to get to know them, all they see is when it's convenient for them to reply.
Sometimes people go on a date and have a great time and then they just don't go back on the app. Likewise, sometimes people go on the app and they only need about 24 hours to feel like that was a huge mistake and they don't come back.
And as for declining or not responding to a blurb. I feel that's completely fine, you don't even need to reply. Not everybody is for everybody, and it's not your job to soothe feelings. Swiping the other way, or ignoring, is a clear sign you're not interested, and that's all is required in the adult world.