Quite a few people arguing for change were murdered/killed. Boris Nemtsov and Alexei Navalny for example. I guess those aren't very intellectual but the intellectuals are probably keeping their heads down to avoid similar fates.
Anna Politkovskaya was an anti Putin writer, also killed by poisoning.
Kasparov is fairly close. "Although I'm half-Armenian, half-Jewish, I consider myself Russian because Russian is my native tongue, and I grew up with Russian culture." He's written a well reviewed book and not been killed just yet. https://www.amazon.co.uk/Winter-Coming-Vladimir-Enemies-Stop...
Anna Politkovskaya was an anti Putin writer, also killed by poisoning.
Kasparov is fairly close. "Although I'm half-Armenian, half-Jewish, I consider myself Russian because Russian is my native tongue, and I grew up with Russian culture." He's written a well reviewed book and not been killed just yet. https://www.amazon.co.uk/Winter-Coming-Vladimir-Enemies-Stop...