Earlier quoted context omitted.
> I still have significant traffic at some clients from IE9 It's been 15 years since IE9. Where do you draw the line?
Depends on the revenue they bring vs the cost of serving them. It's highly dependent on market/business/company. Often you simply don't offer the feature. E.g 3d rendered previews may not be available but product configuration and cart keeps working on a shop selling custom showers (you fallback to dynamic static images). In real estate a page displaying fancy maps with price statistics by area/neighborhood might be…
Fifteen years! Unless it's a government agency what's the point even in doing business with a company that uses 15 y.o. browser? They will pay you in silver coins according to 2011 prices.