Currently the Settings app in windows doesn’t have the same level of features as the control panel does. It’s definitely got most features that normal users will need, but if you’re a power user or a system admin, you’ll quickly find yourself having to swap over to control panel to configure anything past the very basics for quite a few different parts of windows. This change will be fine if Microsoft achieve feature parity between settings and control panel, so that there’s no lost functionality when they get rid of control panel.
I think most people are a bit upset at the idea of the control panel disappearing because they don’t trust that Microsoft will end up reaching that feature parity, leaving people with less options to control their own devices effectively.