Yes, you can sell and buy a different index. However, those who buy ETFs want broad market exposure without picking stocks (or ETFs). Also selling and re-buying means you have to pay taxes now - depending on jurisdiction, that is way worse than holding till you are retired and then selling.
SpaceX/Nasdaq want to distort the rules to make more money off the backs of those passive investors.
SpaceX/Nasdaq want to distort the rules to make more money off the backs of those passive investors.