What you’re describing is not what the OP is asking for. He simply wants a quick solution to block a couple of devices from accessing internet.
I don’t get your “note” as that’s precisely what I suggested the OP to do. And if you actually read the manual and pick a recommend model it can be as simple as uploading the firmware using the router’s firmware upgrade feature.
The scenario you described can be done with OpenWrt on a consumer router and it isn’t that complex to setup. Even older hardware like the Netgear R7800 will be able to handle that.