Not getting the correct speeds that we pay for

I was using a Motorola mb8600 and just bought a arris s33 with no difference in performance 

I see, Me i used before Arris sb6190 or something before forgot the numbers but it was not good for the speed, so i got in 2019 the netgear cm1100 docsis 3.1 and with asus rt-ax86u, but i am having a light blinking on the netgear model "Downstream light blinking" witch not supposed to. First I replaced a splitter outside with the exact what xfinity put, and reset the modem, then verified the firmware if is the latest and still getting the light blinking for the downstream after some hours or a day later. Posted to Netgear forum and they said based on the modem logs that problem maybe with wiring from street to switch, called xfinity they check from their computer and said everything works as it should. Doing other testing (with modem connected directly to my tower pc, no wifi) i notice that the speed test with antivirus program (Kaspersky total) off will increase from 600mb to around 850 to 900mb. (I am on 1200 mb plan 1.2gb). Now when i talked to xfinity they said that my modem is from 2019 and maybe is time to get a new one. I am thinking that something is up with the modem, so is time to hunt other one maybe litter more money if worth it. I may have to look at the approved and recommended list on their site to see what they recommend to buy. Trouble shooting goes on... 

Hello @user_lauw6c, thanks for reaching out for help with your connection. Our team will be glad to take a look at this in more detail. To get started, please use the chat icon in the upper right to enter Direct Messaging. Once there, type "Xfinity Support" in the to line and select "Xfinity Support" from the drop-down list to send us a message with your full name and address.