You compare services to products here.
The market doesn't appreciate disruptive changes to services, hence all improvements done in services of both Apple and Google are iterative and subtle, additive not disruptive.
Such changes are usually also not newsworthy, unless one has to do leaps to catch up with a competitor (looking at you, Apple Maps)...
Google only has a few consumer products, but they made quite a few leaps in the past years for similar reasons (Pixel Phone has to catch up with Samsung, Pixel Watch has to catch up with Apple Watch), while Google/Nest Home is competing mainly with Amazon in an ecosystem war I'd say.
One could argue that the iPhone is not moving forward much in user-experience for a few years now, it's mainly iterating to achieve further cost-reduction/profit and enhance additional revenue streams of Apple.
- Apple Watch is mainly getting enhanced to create additional (healthcare/insurance/services) business for Apple.
- The iPad is under no stress to evolve other than cost-reduction in HW/SW development by harmonization with the iPhone, main strategy seems to be to push customers towards more expensive variants.
- The Macbook was indeed revolutionized, by applying the same supply-chain practice of the iPhone. Lots of leaps forward here in terms of tech, something only Apple could do. But Apple was also not leading this segment and is under strong competition, so they were forced to do something or dissolve into oblivion.
- The Desktop-Mac trajectory seems to be to become a MacBook without battery.
There's an easy explanation for that UX stagnation in iOS: iOS-products are actually not classical "products" anymore, but equipment for consuming services. The devices come bundled with a few free services from Apple and encouage you to consume other services from affiliates.
Apple's main incentive is then not to sell new hardware, but to rollout new enabler-HW for selling additional services.
And they are in an increasing struggle to keep consumers "entertained" to pay for new enabler-HW, so apart from keeping control over their supply-chain they now need to become more exclusive in HW-components to lock-out competitors. Of course that can all be beneficial to the consumer, but would Apple move forward if they weren't forced by their business model?