Earlier quoted context omitted.
Entirely dependent on location, lifestyle, family status, etc. Yes, with $2m you can retire tomorrow and get something like $100K/year in pretty much guaranteed income not pegged to inflation. (You can argue the numbers but certainly ADDED: Yes, you're "rich" but not jet-setting in business class at resort hotels, multi-million dollar coastal city condo, eat at top restaurants on a regular basis etc. rich. Which is a…
Wait, how would you guarantee 5%? I don't see "put it in an index fund" as "pretty much guaranteed".
Past performance does not promise future results, and the world could end tomorrow, but it's not a bad idea to plan that you'll get an average of 5%+ on market investment.
(I'll note that you're responding to someone saying "pretty much guaranteed" and dropped that qualifier in your question).