> There's no reason for Safari to have a sub-par experience except for the laziness of some web developers.

How about a browser with a captive userbase that has less incentive to stay up to date with web standards?

Your argument is that we should expect developers to target/test their app on many different browsers where any random CSS property behaves differently. They will have to buy a device just for this purpose. Because it is obviously developers who should have to pick up the slack here, not Apple.