The Poles, who had fought bravely in a 1-1 draw with Russia on Tuesday, never showed the same application in a game played in very wet conditions.
"We did what we could do. I don't know how to explain the fact that in one game the boys played like they were fired up while in the second game they didn't," Smuda told reporters.
"It is the end of this great adventure".
Poland were hampered by the fact that they had automatically qualified for the tournament as co-hosts and did not get the chance to improve their performances in competitive matches.
In hindsight, their failure to reach the quarter-finals was perhaps sealed in the first game when they allowed 10-man Greece to equalise and escape with a 1-1 draw.
"All in all, we had great moments during this tournament and all we can say is 'Thanks'," said captain Jakub Blaszczykowski, scorer of a thunderous goal against the Russians.
"This is the kind of a moment when one needs to say we need to move on, rethink everything, but such experience is essential," he told reporters.
Poland finished bottom with two points behind Group A winners the Czech Republic, Greece and Russia. Co-hosts Ukraine play England in their final match on Tuesday.
