In this comic, Miyuki is unhappy not because she does not like fanservice. She is unhappy about the Larry Nassar scandal that revealed a huge abuse scandal in USA Gymnastics as well as the mistreatment of homeless people in Tokyo by the police that is evicting them from the Olympic Games venues. That's why she is protesting against the injustices relating to the Olympics.
If you want to know why Miyuki is wearing Rosalina's leotard, that's because Rosalina does not wear her leotard from the Rio 2016 Edition of Mario and Sonic at the Olympic Games in the Tokyo 2020 Edition, and therefore, Miyuki can wear it. The reason Miyuki is holding a protest sign while wearing a leotard is because she stands in solidarity with gymnasts who had been victims of sexual abuse. Miyuki is also protesting against the injustices that nojukusha (Japanese slang for homeless people) are suffering from due to police brutality, which also led to the unlawful arrests of activists, one of whom goes by the name of A-san, whose arrest in 2016 for obstructing "official duties" was considered an unforgivable injustice.
Perhaps the Olympic torch relay was a mistake when it was first introduced, and the Olympic torch relay did not even originate from the Ancient Greeks that conceived the original ancient version of the Olympics at all. Yet another reason for the Olympics to be cancelled and abolished. For all the good intentions the Olympics promised, including peace, we had received almost nothing from it...
Update: The delayed Olympic Games in Tokyo has gone ahead as planned and concluded as scheduled. The campaign to cancel it was not successful.
