I have always wondered why after I use the pull down notification, why did you all change it so it not only doesn't clear the notification, but the notification acts unread, making my LED indicator blink unless I swipe the notification away.
I have the galaxy S9 SM-G960U. When a Samsung Messages app message comes in I can pull down the notification panel and tap the little down faceing chrvron to expand it. That has an option to mark it as read, reply and clear. Same thing on the lockscreen. Mark it as read and swipe it away. Sometimes people are in the middle of something and want to take a quick look at who sent it and come back a little later, read and rely to it without opening the messages app.
It should go away when you tap it or swipe it. You will still have the notification on the badge, like a 1 on the messages when you have a new text just to let you know that you have a new text, but tapping or swiping "should" clear the pull down and the blinking. The badges an be taken off if you would rather not have the 1 on your text message app, in settings under App Icon Badges.
I think there are some people that reply to the sender and wait for the sender to reply back and then keep sending back and forth until its over without ever opening the messages app. I prefer to use it to open the messages app or just clear it if it's not important. Clearing it automatically stops the blinking led and leaves it marked as unread in the messages app.