Captain Magdalena Stysiak, who top-scored for Poland with 28 points, said the team still had work to do to close the gap on the world's best sides.
After losing the opening two sets, Poland came close to forcing a decider, but Serbia proved the stronger team.
She described the defeat as "a big lesson" and said it was "a good sign for the future."
Stysiak added that reaching the semi-finals was an achievement, with Poland making the last four for the first time in seven years.
Libero Justyna Łysiak, who stepped in after Aleksandra Szczygłowska was ruled out by injury early in the tournament, said Poland had struggled to deal with Serbia's counter-attacks and long rallies in the opening two sets.
Hosts Türkiye retained their European title with a 3-2 win over Italy in Sunday's final in Istanbul.
(ał)
Source: PAP