You'd be surprised how easy it is for teams to do the wrong thing. Most people have too narrow of a focus, not enough perspective, and not enough wisdom to even care about the right things. Without people with experience, vision, and influence often times the right things just don't get done.
Being nice means not being ruled by your emotions and not slipping into pettiness. If you have a disagreement with someone, do it nicely. Give people the benefit of the doubt. Etc.
But on the other hand, sometimes it's necessary to do or say things that are unpopular or difficult to accept. The difference is doing the unpopular thing that is necessary vs. being mean because you can't control your temper or you're just a jerk or you're trying to "win" some stupid technical argument. Don't be a jerk, don't yell, don't belittle people, but absolutely call people out on their shit when necessary.
Being nice means not being ruled by your emotions and not slipping into pettiness. If you have a disagreement with someone, do it nicely. Give people the benefit of the doubt. Etc.
But on the other hand, sometimes it's necessary to do or say things that are unpopular or difficult to accept. The difference is doing the unpopular thing that is necessary vs. being mean because you can't control your temper or you're just a jerk or you're trying to "win" some stupid technical argument. Don't be a jerk, don't yell, don't belittle people, but absolutely call people out on their shit when necessary.