Sure, it's called a 'dress code'.

The "baseline" means nothing. The percentage in caniuse means nothing. The only number that matters is the number of Safari users stuck using a no longer supported Apple device that access your website. Of course Apple makes sure to hide usage stats of older devices.

Everyone complains about only having three browser engines out there, but I'll be happy to go down to two if that means freeing the world from Safari.

Whether 98% is acceptable, it depends on the cost of failure, not the percentage itself.