Norway's Karoline Simpson-Larsen won the stage, while American Jessica Diggins secured overall victory in the prestigious cross-country skiing series.
Diggins finished second on the day, eight seconds behind Simpson-Larsen, with Norway’s Heidi Weng third.
The final stage traditionally ended with a punishing climb up the Alpe Cermis ski slope.
Rucka-Michałek, the top Polish finisher, crossed the line 2 minutes, 14 seconds behind the winner.
Countrywoman Monika Skinder placed 24th, while Magdalena Kobielusz was 41st and Aleksandra Kołodziej 45th. A total of 45 skiers finished the race.
Diggins won the Tour de Ski for the third time in her career, having previously claimed the title in 2021 and 2024.
She finished the overall standings more than two minutes ahead of her closest rivals. Austria’s Teresa Stadlober placed second overall, with Weng third.
Rucka-Michałek finished 25th in the overall Tour de Ski standings. Skinder was 29th, Kołodziej 43rd and Kobielusz 44th.
Among women, Poland's Justyna Kowalczyk and Norway's Therese Johaug remain the most successful Tour de Ski athletes, each having won the overall title four times. Johaug has reached the podium eight times.
In the men's competition, Norway's Johannes Klæbo claimed his fifth Tour de Ski title, becoming the outright record holder. Switzerland’s Dario Cologna previously won the series four times.
Klæbo finished 30.1 seconds ahead of compatriot Mattis Stenshagen in the overall standings, with another Norwegian, Harald Østberg Amundsen, third at 1 minute, 8.2 seconds back.
Poland's Sebastian Bryja finished 54th overall, Piotr Jarecki was 66th and Maciej Staręga 68th.
Stenshagen won Sunday's men's 15 km freestyle mass-start stage. Klæbo finished 12th, while Bryja placed 50th, Jarecki 60th and Staręga 69th.
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Source: Eurosport, TVP Sport, PAP