Well they should care for chemistry because it brings championship. This is the foremost goal of a team owner, to be the champion and they can't achieved it without his team blending together to meet the goal. But yeah, GSW doesn't have the ceiling anymore to bring in another caliber player without sacrificing the current roster.
Chemistry can be build along the way. If on the way, the chemistry didn't turned out to what is was supposed to be then definitely that's the time we can called that there's no chemistry on that newly added players on that team.
We can't say right now that there's no chemistry once a newly player just arrived at their team. Like I said, it will be build along the way so for me I will give about 10-15 season games as a test.