Hasn't this been obvious ever since the iPhone become popular?
Apple are very keen on The Ecosystem, because it gets people through the door and keeps them in the room. iPhone is the lowest barrier to entry into The Ecosystem, so making the Mac look and act like an iPhone makes perfect sense. And I'm ok with that. Being able to run iPad apps on my MacBook is great. Even when it isn't a perfect experience, it's good enough to achieve what I need to achieve.
But crucially, I can still use macOS the way I've used every iteration of OS X since my first MacBook in 2007. I can still do the things I need to do without the OS getting in my way the way iPadOS does. And as long as Apple maintain that distinction, I don't really care what it looks like.