Generally I use something else anyway, so even if I were stuck on one of my older phones, Safari would not be the browser I'd be using.
I hate Safari with a passion…doesn't matter what platform, it's all equally bad.
Whether you like Safari or not hardly matters. Apple isn't alone in withdrawing support for browsers running on older OSes. Is it in a developers best interest to devote expensive staff time to updating iOS 9 or iOS 10-compatible versions of their software? With a user base that is tiny now, declining in size steadily, and with no prospect for ever becoming larger, what motive do developers have for cranking out security updates for those barely-used OSes, other than "public spiritedness?"
Whether we're talking about Windows, Android, iOS, macOS, Linux... support for older OSes is going to be cut off after a certain number of years. Once those OSes and/or browser versions stop receiving security updates, developers of secure websites are going to block those OSes and/or the older browsers that run on them.
https://david-smith.org/iosversionstats/ has lots of numbers on OS utilization. It doesn't pay a very pretty picture for older OSes and hardware.