Haven’t seen the film yet, but I can’t imagine it being that good, only because there’s too much story to stuff into two hours. I highly recommend the 1979 mini-series, with Alec Guiness as George Smiley:
You are right about too much story to stuff into a 2 hr. film. And their portrayals of the characters were flat. It was hard to raise an ounce worth of empathy for any of them, much less keep track of who is alive and who is dead with all the flashbacks.
“Red” with Helen Mirren and Bruce Willis, John Malkovich, & Morgan Freeman in 2010 was a story along the same lines, but much better done. Much better.