admin access to XB7 modem for static IP address

My Xfinity XB7 gateway previously allowed local admin login at 10.0.0.1. I had swap it recently because it was discolored due to showing overheating I guess. The new modem does not allow me to login as Admin. I need to assign static IP addresses to some devices connected as LAN. It now forces me to use the Xfinity app, which does not provide DHCP reservations, LAN subnet control, or advanced router settings. This is a loss of functionality for equipment I pay monthly for. I request restoration of local admin access or an alternative gateway that supports full LAN management.