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.
This is a wrong assessment. Barcelona could not win not because they were not serious or aggressive and only wanted a draw but this was all because Atalanta played very well and solidly in every line. So it is wrong to say that Barcelona is comfortable with a draw, they definitely want to be at the top to increase their confidence, only in this match they failed because Atalanta's game was very good.
Atalanta is a strong team, especially Atalanta since being coached by Gasperini. Because in my opinion Atalanta's level has increased, no longer an ordinary or middle team but a top team. From the way they play, their mentality can no longer be called an ordinary team. When facing Barcelona, they dare to play openly, even when facing other big European teams. Atalanta has faced PSG, Real Madrid, Barcelona, Liverpool but they did not look inferior in the slightest in front of these teams and even dared to play openly. Last season they even managed to beat Leverkusen in the European Cup final. In fact, Leverkusen last season was a phenomenon, winning the Bundesliga without being defeated, but in front of Atalanta they could not do much. So Atalanta since being trained by Gasperini is indeed difficult to beat.