Poor Wired/Wireless - New Modem Persistent Restarts

Hello,

The home has been having issues with the past 8 months with poor performing internet.  I've replaced my Comcast approved own modem with Comcast approved upgraded modem, replaced the router, not moved to Xfinity's own modem/gateway and still having to persistently restart the modem for service temporarily.  The xfinity assistant is useless outside a restart and speaking to a human and telling me your services are fine.  I've measured the signal coming into the home and numbers appeared to be low and had a new line installed in March, but still issues persistent.  I'm on the 1200MB package and lucky to get 800MB on the down wired into the gateway and WIFI next to the gateway on 4 different wifi devices 300MB in the down.  I've replaced the splitter in the home to a Comcast approved/came with a home install kit and still the same issue.

I'm not sure if others are experience this same issue with poor wired or services not even reaching the obtainable 1200MB.  Open to thoughts on next steps outside of switching providers.  Been a Comcast customer for near 20 years.