It is not controversial here, but the view is that the USSR should have cut off the more troublesome countries, like Poland and Hungary, and focused on China-style economic reform, and it is pretty common, btw.
Simeon being a bad tzar by being obsessed with the Byzantines and trying to push too deep into their territory instead of going after easy pickings to the north and north-west.
Boris holding out and playing the Byzantine patriarch against the pope to get more western support and a more autonomous Catholic church into the country.