Silkwood is one of the best films of Mike Nichols.

You have to remember, the events this film dramatizes took place in the early 1970's. Workers didn't want to rock the boat & risk their jobs over safety concerns. It sounds unbelievable today, but back then, that's the way it was. That's why her own co-workers shunned Karen.
As for the pacing, it couldn't be much different that the way it was done. In real life, Karen Silkwood wasn't a super hero running around to save the day. She had to sneak & spy. There is no way to depict it better. As for the characters & relationships, Kurt Russel leaving the plant wasn't discussed directly, but he had brought over a friend (when Karen was sweeping the floor & Dolly was cleaning the weed) & he was mentioning opening his own garage, which he did. The relationships may not have furthered the immediate plot of the nuclear plant issues, but the movie was about Karen & her relationships so it makes sense to have character development & understand that Dolly was in love with Karen & had to deal with the fact that she could only be friends with her when she wanted so much more. That was an important part of the movie (albeit made up since there never was a Dolly........she's a composite of a few real life friends/acquaintances & the real roommate Karen had)
I read a book about Karen Silkwood before this movie was even made (I was around 15 when I read it & am 39 now) so I think I really was able to get into the movie because of the book. Give it a read. It's called The Killing Of Karen Silkwood by Richard Rashke (I think that's his name). The woman was & is underappreciated for what she did with bringing attention to nuclear plant safety (remember, Three Mile Island happend a few years after her death) and worker safety issues. A lot of things that we take for granted today, were pushed to the forefront by Karen. RIP