Not as smooth as Apple.

I don’t know if that’s still true. The Music app is still sluggish, Notes has poor UX, almost every built-in app has a better third-party replacement. It has been downhill since iOS 7.

What the replacements for contacts and clock would be?

Contacts+ and Cardhop are two.

To be fair the clock app is a lot better since they introduced the sleep schedule, but I used to have a separate alarm app, and still use Sleepytime to calculate wake up times.

What's so poor about Apple Notes? It's my most used app. Just curious.

And in all 3 cases, the Google equivalents are worse. History shows they’ll probably just be replaced with a different product to solve the same problem which will be worse in its own ways.

Subjective, but I use both Android and iOS daily. Interesting byproduct of Android being the favorite of those obsessed with customization is that the stock apps are almost universally bad because everyone just replaces them with different niche alternatives.

Has it ever been the case that the built-in apps are the best in their category? Should it be the case? Apple's strategy seems to be to make a simple offering that appeals to most people, and to leave the advanced/special/power features to third-party developers. I think that's a pretty healthy arrangement, though I bet many devs would prefer Apple not offer defaults in some categories at all.

until the product gets killed