The Swedish striker came off the bench to restore Liverpool's lead in Istanbul on Wednesday, but the Reds ultimately suffered their first defeat of this season's Champions League campaign.
Trey Nyoni had opened the scoring midway through the first half before Mason Greenwood equalised with a deflected free-kick. Isak then put Liverpool back in front after the break, only for Archie Brown to make it 2-2 before Vedat Muriqi headed home the winner in the 79th minute.
Isak was pleased to find the net but felt Liverpool should have taken considerably more from the match.
"It's never easy here but today I think we could and should get more out of the game. It's a bit sloppy that we had the lead twice and for us to then lose the game is not good enough. Obviously we're going to be disappointed from that," he told the club's official website.
The forward also highlighted the importance of making the most of their goals, particularly in an intimidating atmosphere at the Şükrü Saracoğlu Stadium.
"The atmosphere is really good and it's tough, of course. So, the one thing you can do to keep them quiet is score goals. So, it's a shame that we conceded quickly and we should capitalise on that. That's where we were lacking today."
Isak's goal was his first in the Champions League for Liverpool, having arrived at Anfield from Newcastle United. However, the result took some of the satisfaction away from the achievement.
"I was happy with it at the time. I was hoping that it was going to lead to more. I'm always happy to score goals but today we lost, so it takes a bit from it," he said.
Liverpool have now suffered back-to-back defeats, but Isak believes the situation remains recoverable if the team responds in their next fixture.
"I think we've put ourselves in good positions, so that today if we lose this game it's not a chaos situation. We just need to get back to winning ways, and if we win the next game we are back to a really good position."