Barcelona tried their best in this match, though Atalanta did well too, and they tried their best to see that they win the match, but unfortunately it ended in a draw. I think this could be a very good result for them if they win the match, although the result did not affect Barcelona since their position in the table is still okay. But Atalanta were trying their best to see that they win so they will qualify. But you are right; they can still do better in the coming round. Since they are not a weak team.
I doubt what Barcelona played yesterday was actually their best, considering the fact they had the most ball possession and shots on target in both halves of the game, because what I felt yesterday was that Barcelona was literally just too relax and never played aggressively just same way they played with Real Madrid few days ago,which was actually a strong team. Because if Hansi Flick really meant to win yesterday's game, he would have came up with a workable strategy, as it's obvious what they wanted was a draw.