There were some significant problems with the Roman Catholic Church that it was not solving itself during the middle ages. The Reformation seems like overkill in some of it's extremes, but the problem is that people like Erasmus (Who was sort of the forerunner of Luther, but who refused to leave the RCC) had no voice in the Church. If you stayed in union with Peter and protested, you were sidelined. Luther I think wound up on trial before he split, didn't he? Some people may have even wound up in prison or worse.
The Reformation had it's faults, but I wonder if Christianity would still be around today in the numbers it has if the Reformation hadn't happened. It kept people in the fold in some way, and it forced Rome to eventually reform itself in some ways. It's an inside-outside game. If pressure from the inside isn't working, you go outside, and that creates another source of pressure, and maybe eventually you not only get new churches, but a better Roman Catholic Church.
We'd never have had a Vatican II without the Protestant Reformation.
And in some ways, a diversity of cultural experiences is good. I mean, in the US some places there are Polish parishes or Italian parishes with traditions from the old countries, less so than there used to be, but there. A future reunification doesn't necessarily mean everyone under direct Papal authority doing and believing exactly the same thing, maybe it means means a lot of churches that have different traditions, but share clergy and communion and recognize each other, and has the Pope as the figurehead spiritual mentor without the same doctrinal and governmental authority over the churches.
This is mainly a response to the video rather than the original post, which actually talks about something different if you click the link.