Upgrading to gig internet breaks series x and s network performance

Hi. I bought a series x and upgraded to gig internet speed. My speeds became slower than before I upgraded. I had my ISP come out over ten times and they found no problems on their end. I have replaced my router and modem every time a technician has come out. I saw another question on this forum describing the exact same problem. I have fluctuating packet loss and my latency is over 150ms when I test multiplayer connection and hold all of the shoulder buttons.

:)