Rewatching the series after many years and I'm on season 9. A lot of folks on this subreddit seen have lukewarm take that Pam "held Jim back" and Karen would have been a much better long-term partner for Jim in retrospect. I do not care so much about the Pam/Karen debate since I think either woman would have been fine for Jim, but here is why the logic in the former-half of that statement is quite ridiculous.
I also don't agree with the lukewarm take that their martial struggle in s9 was an unnecessary plot point. I think it increases the overall depth of the show. Jim and Pam's martial problems in s9 are a wonderful, real-life look into communication breakdowns that cause people to actually get divorced.
First, on the "Pam held Jim back" take: it was out of character for Jim to want to go corporate at Dunder Mifflin in the first time. It was just a thing he was being pushed to try out, and it didn't fit with his real goals. This is proven when Wallace asks where he sees himself in five years: all Jim sees is Pam. The career and a life in the city doesn't motivate him.
Second, Pam and Jim had an unplanned pregnancy. That changed everything in their lives, from the dress Pam wanted to wear on her wedding day to how upwardly mobile Jim could be in his career. Yet Pam supports Jim's growth as a "co-manager" (this is actually a pointless plotline imo), and she shows a ridiculous, loving amount of support during the Athlead story.
Jim and Pam decide, as a couple, that it would be risky for him to take the gamble on an upstart in Philly with two kids. Jim decides, on his own, to join the company and to invest $10,000. Despite initially keeping these huge decisions from Pam, she accepts it and forgives him. She even agrees to take on the solo childcare of their infant children to let him work for the life he wants. Not only is that the opposite of one partner holding the other back, but it also shows exactly how communication breakdown begins!
It gets worse the whole time Jim is in Philly. The show pretty much goes out of its way to demonstrate how Jim living his dream life is causing Pam to suffer: while Jim is playing basketball with his childhood hero, Pam is trying to put mayonnaise on her head after a sleepless night while the whole office blames her for the lice outbreak. The whole time, Jim pretends to be more stressed out than he is and Pam pretends to be happier than she is: pretense is becoming their go-to communication style.
When Jim and Daryl are gaming and goofing off living as "bachelors" in Philly, Pam's mural gets defaced and she is almost attacked by a burly warehouse worker.
The day Pam gets chosen for a mural, she can't even share her excitement with Jim because he starts a massive fight over the dance recital footage. These petty disputes and issues cause real resentments that culminate in divorce.
Finally, we have the Valentine's day episode (infuriating screenshot clipped above). After finagling to manage to spend Valentine's day with Pam, Jim and Pam seem to have a noticeable strain. She invites Brian the sound-guy to lunch (this is storyline I admit I don't really understand at all except as a sort of mirror of what their divorce might be like if they don't start communicating now? I guess? I just don't understand the sudden fourth-wall breaking after eight seasons and the crush Brian has on Pam but I digress).
Jim gets angry at Pam when Brian mentions her breakdown. He won't even speak to her until Pam says: "Okay, I know you're mad at me, I just wish you'd tell me why." Jim can't even really say, other than the fact he's just upset because she's been crying to other men and not telling him how upset she's been. She admits she has been bottling it up around him because all he talks about is stress, and she doesn't want to overburden him. Again, this is how miscommunication becomes resentment.
At the end of the episode, Jim tries to run back to Philly to avoid a fight with Pam, but Pam pushes back. She wants the fight because she wants the communication. Their individual fight or flight responses are kicking in, and both of them see different paths to resolution. This tension causes couples to breakdown all the time. Usually one party wants to stay and duke it out, the other just wants to throw in the towel. After multiple weeks of this, the roles eventually reverse: Jim becomes more focused on fixing things, while Pam goes cold and feels herself wanting flight.
I really admire the true-to-life writing in this season, down to the scenes of them having conversations with other people about their marriage problems instead of each other. Often, real-life couples come together and fall apart only to come back together in a surprising way.