Perhaps you haven’t noticed but Safari has shipped about 20 updates in the last 3.5 years.
If you check the Interop 2025 numbers, you’ll see Safari is neck and neck with the other browsers and has implemented the latest CSS features [1].
The WebKit team was first to crack the code on how to implement :has() that eluded browser teams for 20 years and was the first to ship it [2].
As for wishing that they didn’t have to maintain Safari, it’s a mission critical framework on macOS, iOS, iPadOS, visionOS… it’s the only thing saving the web from the monoculture of Chrome-based browsers; unfortunately Firefox is in the low single-digits as far as market share goes. Safari on iOS has about 25% market share.
Safari has long lagged on other browsers, Apple would rather it didn't exist but have to keep it ticking over
With less competition they will likely be happy to lag behind even further again