Those who don't want to take some responsibility for the sins of their colonist
ancestors should think about forfeiting their inheritance
of the wealth and privilege
those sins made possible. And I'm not just talking about individual family wealth; there's social wealth in the form of public infrastructure, universities, hospitals, and the like, which have been developed thanks to the wealth of stolen land, designed to benefit primarily (often exclusively) the descendents of the colonists. A collective will to forfeit (some) of that inheritance would result in moderate reparations
to descendents of the colonized.
Your ancestors doing horrible things doesn't make you a worse person than anyone else. But distancing yourself from their acts, while refusing to relinquish anything that you've gained from those acts is reprehensible.
Almost any idea taken to its extreme can be made to look ridiculous. Unlike your examples, we are talking about identifiable groups of living people, and crimes that didn't start all that long ago (especially in the terms you have set) and are still going on. It's possibly debatable whether they're still going on in the U.S. and Canada, but they are certainly many living people who were subjected to genocidal policies. I know native americans from New Mexico my own age whose parents were forced into a boarding school system that was designed to destroy native american culture, where they were harshly punished for speaking their native languages.
I don't think there's any credible group seriously suggesting that white people should leave North America, or anything remotely like it. But is it too much to ask that we acknowledge that Native Americans (and African Americans, latinos, and asian americans too for that matter) have been wronged and deserve a bigger piece of our collective wealth and privilege? And then we can reasonably discuss what steps can be made to create improved conditions for groups that have been (and still are) discriminated against, equal opportunity, and better inter-ethnic relations.
Your argument that "At one time or another, every culture has moved into the territory of another culture and taken it for themselves," doesn't justify anything. Just about every culture in history has enslaved their enemies, killed religious heretics, persecuted homosexuals, and believed that mental illness was caused by supernatural possession.
You are correct that putting a monetary value on the damages is difficult. How much? Who owes it? Who is owed? But there are many choices between 'trivial' and enough to 'bankrupt nations'. And, by the way, I don't think the groups asking for reparations consider their proposals 'trivial'.