Sounds like you’re on the right track with a new router. It sounds like you’ve plugged directly into the modem via hardware and gotten 220 Mbps, which clearly indicates Spectrum is delivering 200+ Mbps to your home and your device is not limited to 100 Mbps.

If you plug your device in to the router’s wired LAN ports and it drops down to 100 Mbps then chuck the router. Same thing happened to me, Comcast delivers gigabit to my outlet. Confirmed directly at the wall. There’s a bit of overhead when plugging directly into the modem but I still got the substantial majority of that speed. I had an Asus RT-AC68U and despite being advertised as having gigabit LAN ports, the hardware wasn’t actually capable of delivering those speeds. Not sure if it was lacking CPU or RAM or what, but I topped out at about 300 Mbps after plugging the router into the cable modem and my computer into the router. Bought a new router and now I’m cruising at 750+.