I would assume a little of both. I've seen weeks wasted just because someone wouldn't say "that's a bad idea". I've also seen whole projects turn to crap, and then get canceled, when people that new better decided to remain silent, to avoid conflict.

Through my years, it seems to be increasingly rare to find disagreeable people, and that agreeableness is being favored/demanded. I'm not one to judge if it's working or not, but when I see people getting upset at managers because the manager criticized their work/explanation during the presentation of that work, which is literally meant for criticism, I know quality coming from that group will be impacted. Maybe not surprising, but many of these people are new graduates. The few "senior" people I know, like this, are from companies who are in the process of failing, in very public ways.

I think the ideal scenario is a somewhat supportive direct manager, and a disagreeable, quality demanding, manager somewhere not far above, keeping the ship from sinking.

I don't work in IT, but in the medical field. We have the advantage/disadvantage of working in many teams during our training (around 20-30). There are varying cultures in teams, and what I found was that teams with high levels of criticism / conflict generally functioned the poorest. Patient care was delivered despite the dysfunction and toxic culture, but it also created an environment where staff were unhappy, fearful of mistakes, and avoidant. The best and most effective teams I worked in had a less hierarchical structure, but were led strongly, with good team working and communication.

That's anecdote, but there's evidence that certain team styles lead to more effective work [1], and suggestion that serious failures of organisations relate to cultural workplace toxicity and leadership [2].

I've seen in the thread a slight strawman argument that 'people too timid to say what they think about something leads to poorer working' or similar. I totally agree with that, but good communication is not what we're talking about here, and people can be clear, confident and respectful.

[1] https://www.civilitysaveslives.com/theevidence [2] https://blogs.lse.ac.uk/politicsandpolicy/30566/