I haven't seen the movie (although I really wanted to because of Saoirse Ronan) but I've been monitoring the movie's reception, and it's had sort of a peculiar drop in positive feedback as opposed to the first 28 critics or so that reported in to RT by the early part of this month
https://web.archive.org/web/20181201022627/https://www.rottentomatoes.com/m/mary_queen_of_scots
December 1st, 2018 - 28 Critics - 93%
Critic Consensus: Mary Queen of Scots delivers smartly crafted period political thrills while offering a brilliant showcase for the talents of its well-matched leads.
https://www.rottentomatoes.com/m/mary_queen_of_scots
December 30th, 2018 - 158 critics - 61%
Critic Consensus: Mary Queen of Scots delivers uneven period political thrills while offering a solid showcase for the talents of its well-matched leads.
If you want to see the other saved archive pages and the movie's general trajectory https://web.archive.org/web/*/https://www.rottentomatoes.com/m/mary_queen_of_scots
Also where's the /r/movies discussion thread for Mary Queen of Scots?