Safari is awful on the scale of being a 2nd tier browser like IE. It's the browser people use because they don't know any better, or because they don't have any choice.
Safari isn't a competitor with Chrome, Firefox, or Edge
I switched from Chrome to Safari as my desktop browser a few months ago. I kind of miss uBlock Origin, but other than that I have zero regrets. Safari is noticeably faster, doesn't kill my battery, and the company that makes it isn't continuously trying to sneak in privacy killing features. Instead, every version Apple ships includes more default settings to make my browsing more secure and less trackable. It's a great browser.
I still use Chrome for google stuff (e.g. gmail, google docs, GCP, etc), but that's because google has chosen to make their own properties work poorly in other browsers.
Maybe something to do with hardware accelerated h.264 decoding? (Assuming YouTube serves VP8-encoded videos to Chrome users and h.264 ones to Safari users.)
Safari got a reputation of being "the new IE" a few years ago because it was lagging in standards support. However there's been a lot more progress recently - coinciding with when they started releasing Safari Tech Preview builds.
I guess it's fair to say the latest Safari's are much better, but over the last few years our web team definitely cursed Safari for issues more often than we've cursed IE.
I actually really enjoy using Safari, and I am not alone. The dev tools are great and the main extensions I use are available. Perhaps you can elaborate a bit more on your experiences with Safari?
Of course it's a competitor, I expect it's comfortably the dominant player on the Mac platform. And I find Apple to be the most aggressive of the minor players about addressing rendering issues on major sites.
I still use Chrome for google stuff (e.g. gmail, google docs, GCP, etc), but that's because google has chosen to make their own properties work poorly in other browsers.