You'll notice that it's really only the big tech that lean towards simplification. Small indie devs want to cram in as many features as they can. If an indie project is labeled as "simple", then a) it's often already more feature-rich than the big names, b) only at the beginning of development, or c) if it's designed to be simple, you have a lot of alternative options (see Android launchers).

The big tech doesn't want you to think. They don't want you to have options. They want you to consume.

If you're missing something, they want you to buy their solution: the next generation product, the accessory, or addon, the microtransaction, the subscription.

If you start wondering why your brand new device or operating system is slower than the stuff 1 or 5 or 10 generations before, it's probably because of all the tracking and advertising systems in the background. But you're not supposed to think about that. You're only meant to click at the shiny buttons and consume the app.

Speaking of shiny buttons, I kinda believe the simplification and corporatification of design elements such as icons and logos is part of this. If someone makes a bunch of nice elaborate 3D icons... Well that's art. Art makes you feel and think. The less art is around you, and the more it's replaced by lifeless lines and the simplest of design elements, the more likely you are to just follow the leader and behave. Pretty much the idea of brutalism, frankly.