The former GMTV host, who took part in the show's 2005 series, admitted that she felt disappointed when the plans for this year's run were confirmed this week.
On Thursday, BBC bosses announced that choreographer Arlene Phillips had been axed from the programme in favour of former Strictly champion Dixon and professional dancer Darcey Bussell.
Writing in her column for The Mirror, the TV presenter asked: "Since when was Alesha Dixon a choreographer? And who, outside the chattering class pastures of the broadsheets and the Royal Ballet, cares about Darcey Bussell?"
She continued: "Arlene Phillips, on the other hand, was an essential part of the winning Strictly Come Dancing formula - her caustic comments cutting through the ice of a wintry Saturday night, willing you to throw your takeaway at the TV screen as she lay into a well-meant but hopeless celebrity dancer."
Fiona added that the former panel member is "a decent person" and acted like "a caring mother figure" once the cameras stopped rolling for the BBC One show.
Strictly Come Dancing returns in the autumn.