That's not what's happening though. First off, social mobility is declining, so let's get that out of the way:
http://www.businessinsider.com/social-mobility-is-on-the-dec...
Second, I think it's still a problem if the income of 90-98% of the country stagnates for decades, while the top earners get higher and higher income. Of course that affects inequality.
I'm also not sure it matters that much if the players at the top switch around if they have increasingly larger leverage on society.
For instance, we're seeing CEOs get rewarded larger and larger amounts of money every year, even if the companies lose money, like in this absurd case:
https://techcrunch.com/2018/02/22/snap-ceo-evan-spiegel-got-...
Where's that money coming from? The employees' potential salary increases? The retail investors' money? It seems to me that the rich keep siphoning off money from everyone else, and that's not sustainable.
They also get larger and larger amounts of money even when they get kicked out of the company for failing. This doesn't make sense to me at all. And I think the excuse that they need such amounts of money or otherwise they wouldn't take the job or something is utter BS. I'd more likely believe the board is giving them the money so the CEO doesn't sue the company, or better yet because the CEO was the one writing their checks before that, or something along those lines.
And this is just the corporate world. The US Congress seems to get crazier every year and listening more and more to corporations and their interests, and less and less to the people and solving real problems in the country (healthcare, infrastructure, etc).
It's like the whole American society is on the brink of collapse, and everyone just doesn't know it yet. Eventually, people will "suddenly" start to violently riot because of all this stuff added together, and it won't be pretty.