Getting under 60% is super hard to do in the genre on RT for audience, especially recent films. 63% a year out, and it was at 94% after the first few days from fans who voted it highly out of fandom, before the film came out. So yeah, not the most reliable meter. As likely to dip into 'rotten' territory as it is to stay in the low 60's two years down the line.
Lower audience score than all 14 MCU films, lower than 8/10 X-men films - one percentage over X3, four over Origins:Wolverine - tied with Suicide Squad at 63%, over 10% under it's predecessor Man of Steel, only 2% higher than Supes Returns, lower than every Batman movie not directed by Schumacher, higher than Green Lantern as well as DC's two complete modern day abortions, Catwoman and Jonah Hex.
Green Lantern was in the low 60's until two years out when it dipped to 45%, kind of expecting the same with BvS and SS considering the reaction to those films were fairly comparable to that of GL.