It’s against the EULA, but nobody is going to get caught. The main issue is that it’s a pain in the ass and doesn’t scale. You can do this for one person, but most people aren’t going to be cool sending a payment to an address and just waiting around, hoping that they get a key. This is why Steam exists. There are other services that do the same thing that are not US based. GOG is based in Poland, for example: https://en.wikipedia.org/wiki/GOG.com

It’s not just the obsoleteness of it, it’s the fact that any device that is on the other end of the TV’s HDMI cable would need to be actively routing internet traffic into the HDMI connection. What device would do that? Any device that’s using the TV as output for itself has no reason to also include network access.