That’s just moving goalposts. Developed countries represent the current standard of tech, everything else is just playing catch up, it’s not “progress”.
Scale is important. If a medical breakthrough can be delivered to 1% of the population vs 50% of the population, that is progress that meaningfully improves the human condition and affects how risk averse we are to different diseases. If we deploy electric vehicles to 5% of drivers vs 100% of drivers, that is going to have a tremendous environmental impact that can benefit everyone.
Seriously, if you're rich enough maybe what you say is true, but I don't think you could say "people’s daily lives have gotten as good as they’re gonna get" until poor people in "developed countries" don't have to worry about basic necessities to stay alive.
Perhaps one could strike a couple countries off the "developed countries" list and call it a day, but that list would be much smaller..