So far they're third going by the caniuse score, which is based on the features developers can use. Previously it last place.
I don't think it was the developer backlash that forced Apple to start releasing TP previews of Safari and progressing features. I was likely more of a gap between major versions (Safari 9.x vs 10.x)
Microsoft took 5 years to go from IE6 to IE7, and 7 was really bad. IE completely stagnated, while being the default browser on a billion PC's. Then they were very slow to adopt HTML 5 features. Developers were supporting IE6 over 10 years after it was released. I doubt if many people are supporting 5 year old versions of Safari, let alone 10 year old versions.
I feel like many people have forgotten how bad this really was, or simply weren't developing back then ...
A dubious analogy that works if you squint really hard.
You can't use any truly different browser than Safari on iOS, so until that's possible, I'm hating on it as much on iOS as I hated on IE on Windows.
Even if it's lagging behind less than IE did, I still strongly dislike being at Apple's mercy rather than the users'.