It’s still got popularity within tech-inclined Mac/iOS circles too because it’s easier on the battery than Chrome (+derivatives) and Firefox. Some would like to switch but because neither Google nor Mozilla has much to lose for their browsers being battery hogs, relatively little engineering effort gets dedicated to improving efficiency compared to WebKit (which is similarly efficient under Linux in e.g. GNOME Web, proving it’s not purely first-party advantage).

That’s because Apple adds two extra legs to Safari on OS level and cuts both the legs of other browsers in a manner of speaking by rigging this comparison.

I think the narrative is that once developers have the option to tell all of their users "we only support Chrome, just install Chrome" then any support for Safari will dry up.

Unfortunately I don't think we will see if this is how it plays out until Apple has to allow other browsers globally.