Klopp's side had 22 shots on goal throughout the game but only converted one through Mohamed Salah in the opening three minutes.
"I don't think you can create much more chances, better chances but we don't finish the game off. We didn't play enough," Klopp said after the game.
"In a specific way, we don't fight enough. We had 70% of the ball and should have had 80, we created a lot of chances. So we had to create more and use them. But we don't do that well at the moment. It feels like a defeat.
"I didn't see us that we deserved today to play Champions League next year. But we will see what we can do. In a few days we will play Manchester United which will be a tough one as well. But we learn... or we don't play Champions League. That's it."
Klopp's team have a number of important fixtures on the horizon if they are to qualify in the top four, including facing United on May 2.
Newcastle controversially had an earlier goal from Callum Wilson disallowed and Klopp said his side were "lucky" the decision went in their favour but didn't capitalise on it.
"We have to keep going, keep playing. But we kept them alive and they deserved the goal because they scored before," he added.
"It is another one with the new rules, unlucky for Wilson but it is handball, and we don't even take this present. We were lucky with that decision, but gave another chance away and it makes no sense. It's really tough to take."