But for people born in say 2120, it will be an issue because there will only be 20 years left before in becomes deflationary, but for all of us born now it has no effect.
I get the gist of what you're saying, although in a hundred years, a lot of things might and will happen that what you're trying to say would be trivial, and would not matter anymore. Perhaps by then, the need to use bitcoin would not be there, as it will be replaced by another system that runs better and is more adapted to the society in that century. Right now, the 21 million cap is in place to keep the system from losing value like fiat. Also, the diminishing returns over time ensures that no one can 'whale' the system and if they want to, they'd also need to shell a whole lot of money in order to do so.