It's not just chromium in and of itself. It's that it would be a browser that's unmodifiable by the user, so no unapproved extensions, no ad blockers, etc.

It's a way for google to tell its ad buyers that "hey, we can 100% guarantee the end user is seeing your ads if they're using this browser". And then all of the corporate websites cater only to that browser, or give a different user experience for all other browsers.

Personally, I find this problematic for several reasons:

1. I wouldn't be in control of my browser and how it executes arbitrary code on my machine

2. The system creates second class citizens on the internet

3. It cedes control of the open internet to corporations, like google

4. Privacy; I don't give a shit what google says about pseudonymous and group identities, researchers have found problems after problems after problems...