@Kodikid Everybody's needs and requirements are different. I've got around 30 wireless devices connected at any one time and they're split between the 3 WiFi bands on my router. I then have many of my IoT devices split onto Guest Networks. Same when any guests come to stay, they get the Guest Network to connect to.
My router's settings allow me to change things an ISP router might not (depending on whatever router might be supplied), such as DNS settings on the router itself. So I use Quad9 DNS for instance. I don't want my ISP deciding what DNS I have to use. Yes, granted, you can change DNS settings on your laptop/desktop, but I just prefer to change it within the router settings.
Just recently, I changed the bandwidth for 2.4ghz to 20mhz, not sure if that can be done on an ISP router as it's been that long since I used one. I also set the channels on my router so that I was using the least congested channels on 2.4 and 5ghz (I use inSSIDer to analyse which channels my neighbours are on). As a consequence, my devices don't drop out at all. There are also other settings within the router settings that I can change to suit my needs.
And then there's the security protocols. I have set mine to WPA2/WPA3-Personal. Some routers don't have the option of WPA3 (AFAIK). It might not seem important to many as some may cite that WPA2 is perfectly adequate.
I fully accept that many 3rd party routers aren't asthetically pleasing to the eye for many people. ISP routers are deliberately designed to 'fit in' with 'modern' homes, whatever that is supposed to be. And of course, ISP routers are deliberately designed to be 'idiot proof' plug and play. My router is sat behind my large flat screen TV and no one can see it. And before anyone wonders, no, I don't get any loss of signal to any of the devices on my network.
To address the point about buying a EE router off the famous auction site, well of course one can do that. I personally wouldn't because you literally have no idea where that router has come from, but then again, if you're only paying 20 quid for it, you won't care anyway. There is of course the low risk that you could be getting a router infected with malware, but that's a risk you take. I'm hazzarding a guess that all of the things I've mentioned, you will be completely aware of anyway (others might not). None of it might be important in your environment, but I like the fact I have some sort of control that I might not get with an ISP router.
