I have many nerdy friends who have been Linux users for ages. But most of them don't know such a thing as Openwrt exists or have never bothered to give it a try.
It's a very fun piece of software to play with and can be extremely useful for routing traffic.
Wondering why it isn't more popular/widely used.
In my experience it's because it's finicky as fuck and requires very specific (and often more expensive) router models, and even then it still crashes just as much as a proprietary os router.
sure, and then you have to make sure you get the correct radio accessories, as the built in pi wifi isn't going to do so hot acting as the hotspot for multiple video streaming devices.
Radios which you also have to vet against the approved hardware list for OpenWRT, and having multiple channels is even more of an issue with the lack of USB ports (depending on model)
Then you're still looking at a mess of devices and a relatively power hungry system plus you still have your ISPs modem
I need my Internet for work, so I just replaced my ISPs modem with a FritzBox, which is not ideal, but serves me well, gets updates for quite a while and works pretty much always.