The West Africans, making their fourth appearance at the global showpiece, bowed out after surrendering a two-goal lead in a thrilling 3-2 defeat to the Belgians.
Senegal endured a difficult start to the tournament, losing 3-1 to France before suffering another narrow 3-2 defeat against Norway in their second Group I fixture. However, they responded in emphatic fashion with a 5-0 victory over Iraq to secure a place in the knockout stages.
They looked set to progress after Habib Diarra and Ismaila Sarr handed them a 2-0 advantage against Belgium. But the Europeans mounted an impressive comeback, with Youri Tielemans scoring twice in quick succession before substitute Romelu Lukaku struck the winner in the 86th minute.
Mendy watched from the sidelines after sustaining a knee injury in the group-stage defeat to Norway, with Mory Diaw taking his place between the posts.Reflecting on the tournament, the former Chelsea goalkeeper did not hide his disappointment.
"This elimination is a failure. We had the qualities to go further. We didn't," Mendy wrote on his social media pages."I gave everything to heal my injury and return in time to help the team until the end, but it wasn't enough. Now, we have to have the courage to face reality."
The 34-year-old called for an honest assessment of the team's shortcomings, insisting superficial analysis would not help Senegal achieve greater success in future tournaments.
"A competition of this level demands a deep self-examination. Not a superficial one, but an honest and demanding review of everything that has been done," he said.
Mendy added that Senegal must be willing to confront "the most uncomfortable truths" if they are to compete with the world's elite.
"Senegal deserves a team and a federation capable of turning failures into lessons and lessons into victories. It is up to us to prove ourselves worthy," he concluded.