SB6121 vs SB6183

I just got off the phone with [Edited: "Inflammatory"] India support. They told me I can't use my old SB6121 anymore because it's End of Life. They told me instead to buy a SB6183. When I looked up what it was, it looks almost EXACTLY the same, They're both DOCSIS 3.0 modems, they're both basically the same looking modem, same shell same color different model number. The reason the support staff gave me was that "this modem is only rated for 139Mbps" which is complete nonsense. I remember speed testing it, and getting around 200 or more, which I googled the spec sheet and found this: https://www.speedguide.net/routers/arris-sb6121-surfboard-docsis-30-cable-modem-1170

Boo hoo, I'll lose 100 Mbps from a copper infrastructure that can't even do more than 10 Mbps up, yet wants to brag about 300 down as if anyone cares. No directly peered services from Comcast can even get close to that, when watching YouTube or Netflix I constantly have to buffer or wait, and no I'm not on WiFi, I have a CAT.5e cable running from the X1 modem to my computer. The reason I want to switch to my old SB6121 is the stupid X1 gateway has a [Edited: "Language"] fan in it to cool it. What [Edited: "Language"] is so sophisticated about a DOCSIS 3 modem and WiFi combo that it needs a fan?! My iPhone 6S is passively cooled, you're telling me a device that's able to communicate with space and runs a 1080 screen at 60 FPS needs less cooling than a [Edited: "Language"] modem that processes TCP/IP requests?! WOW!

[Edited: "Inflammatory/Language"]