Nolan, I'm not familiar with what you do or have done, but have you ever tried to make a website back in the day? Ever tried to support IE6? 7? 8? IE literally broke the web. CSS rules which worked in every browser ever wouldn't work in IE. Entire webpages weren't formatting correctly, having to spend hours, days, on workarounds. Comparing Safari to IE is just wrong. Safari doesn't break the web, it 'just' lacks supp…
I think the analogy is very clear. If you want to code like it's 2000, supporting IE6 is easy, because IE6 is a very good 2000 browser. If you want to code like it's 2010, supporting Safari is easy, because Safari is a very good 2010 browser. But in both cases, if you want to use any new features that have been standardized and are supported by other browsers, you're fucked.
The main difference I see is that IE6 didn't get any updates at all. Safari gets updates, but many new features are missing or broken.
EDIT: Another difference is that MS never blocked you from installing a better browser, but Apple does that on iOS. That policy is becoming increasingly ridiculous...