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.
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.
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.