Need to help parents expand wifi coverage, apparently they have MoCA

My parents have a cable provider which gives them TV, internet and phone. The trouble is their wifi AP is in a far corner of their house which gives poor wifi coverage at the opposite end, of course.

Their devices are entirely owned and installed by their provider. After reading about the devices they have, I see they have a MoCA adapter, a modem/router combo, and a telephony modem. I'd like to help them expand their wifi coverage with no interruption to their TV or phone service. I'm also assuming limited or no configuration access to the existing devices.

[Here](https://imgur.com/a/CSYpRAx) is a diagram of their setup. As far as I know, they have no other MoCA capable devices in their home, so I'm not sure what the Actiontec ECB2500C is doing here.

The Arris DG2470 appears to be a modem/router combo so perhaps we could replace it with a standalone modem connected to a mesh wifi network?

If there are cheaper / easier options I'm open to suggestions.