Google seems much too sure of itself making this change. I hope their arrogance pays off just the same as Microsoft's did with IE.
I think it's part of a much bigger trend in tech in general but also in Google: Removing user control. When you look at the "security" things they are doing, many of them have a common philosophy underpinning them that the user (aka device owner) is a security threat and must be protected against. Web integrity, Manifest v3, various DoH/DoT, bootloader locking, device integrity which conveniently makes root difficult/impossible, and more.
To all the engineers working on this stuff, I hope you're happy that your work is essentially destroying the world that you and I grew up in. The next generation won't have the wonderful and fertile computing environment that we enjoyed, and it's (partly) your fault.
That was a world where the user base was much more limited and devices were less capable. Now we have children, grandparents, educated, and uneducated users with access to web connected devices. These devices now contain everything about you. Compromise of a device can destroy someone’s life.
Not only that, but compromise of a device can cause collateral damage to other devices on the same network.
We now have to cater to every user. Not just to the technologically adept. Look at what people believe on social media. The bar is so low to con people into compromising their device.
Write insecure software and you'll get screwed by hackers. Write secure locked down software nobody can touch or modify, and you'll get doubly screwed by a large corporation that wants to pound every penny they can out of your bloody corpse, upto the point your device is compromised by the corporation who can do whatever they want, but you cannot tell.
There is no win situation here, there are only trade offs.