technical support

Some tips for improving WiFi performance;

http://corporate.comcast.com/comcast-voices/10-ways-you-might-be-killing-your-home-wi-fi-signal 

https://www.xfinity.com/support/articles/improve-your-wireless-home-network 

There are other options. Google for WiFi repeaters / range extenders, WiFi mesh systems / pods. Good luck !

https://www.cnet.com/how-to/your-router-isnt-as-fast-as-you-think-it-is-heres-why/ 

https://www.cnet.com/how-to/home-networking-explained-part-2-optimizing-your-wi-fi-network/ 

http://www.metageek.com/training/resources/design-dual-band-wifi.html  

Hello @user_nx0vlx, and thank you for posting your concerns and your experience on our Xfinity Community forums.  (And thank you @EG for highlighting this for us!) 

Comparing your Wi-Fi services from one Wi-Fi router from even a few years ago to a newer one from a different provider can be problematic from a technology standpoint.  The push within industry standards for more speed and the need to have services operate faster based on consumer needs has guided technology development.

Newer routers often have less range because they broadcast on higher frequencies (like 5 GHz or 6 GHz) which offer faster speeds but shorter, weaker penetration. Older routers predominantly used the 2.4 GHz band, which penetrates walls well. Newer routers rely on 5 GHz or 6 GHz for speed, which suffer drastically more signal loss when passing through physical objects.  (It's a bit of a compromise - more range vs. faster speeds.) 

Densely populated neighborhoods have overlapping networks. Newer routers automatically manage and limit their own range (using narrower, higher-capacity channels) to reduce interference with neighbors.  An older router with large external antennas isn't actually "stronger"; it just might be broadcasting an unoptimized, "sloppier" signal, and likely had a slower connection overall.

As @EG helpfully pointed out on this thread, there are steps you can take to help mitigate the issue you are having, such as Wi-Fi Extenders or products like the Xfinity Pro service which you could add to your home networking, which in the case of Xfinity Pro would also give you the added advantage of continuing to have internet access during a power failure or a service interruption.