It's creating a Google monopoly over the web.
Chrome's not open source.
Chrome has light to moderate tracking issues.
Developers are starting to only support one or two browsers (talking about websites not extensions) , which I think is absurd and it reduces competition.
I think Firefox is a better browser than Chrome/ium in a few ways and vice versa.
You're the developer I'm assuming. You've made a great product for a popular browser, so there's nothing to worry about for you, but I think if people switched to Firefox, the Internet would be a better place. Good luck!