Wireless 5G well below, wired and service speed

What devices are you using to test?  Both clients and modem/router/gateway.  Please be as specific as possible.

What sort of place do you live in?  WiFi being slow when your wired speed is much faster is often caused by interference.  Apartments, condos and townhouses are particularly bad, especially if they have frame walls between units.

It's quite possible the WiFi router/gateway/mesh node/AP/etc. is just misconfigured or autoconfigured itself stupidly.  There are tons of complaints on this board and across the internet in general about brain-damaged WiFi auto-configuration.

WiFi 5, 6, and 6e support channel widths of 20, 40, 80 and 160MHz.  A lot of devices don't support 160Mhz channel width.  They also have more than one stream.  Max bandwidth is based on width x streams.  Most clients only have 2 streams.  Fancy routers have more.  I don't know how many streams Comcast gateways have, but even if they have more than two it's not likely to help unless you have one of those rare few clients with more than 2 streams.  A few laptop and desktop WiFi adapters have more than 2, like more recent and higher end Intel based MacBooks have 3-stream WiFi 5 radios.  I'm not aware of a phone with more than 2 streams.  Sometimes autoconfiguration does something really stupid, like picks a channel with a lot of interference or decides to use a 20MHz wide channel.  For example, if you're using WiFi 6 or 6e with a 20MHz wide 5GHz band (or 6GHz for 6e) channel with the usual 2 streams 200 is about what you would expect.  Max theoretical bandwidth in that configuration is 300Mbps, but you never get max theoretical on WiFi.  The rule of thumb is 2/3s is fine and 3/4s is pretty much max if you're close to the router/gateway/AP/etc.