I used to use apps on my Samsung TV, but it became clear that Samsung wasn’t interested in ensuring that the device was secure, so I had to look for alternatives. They stopped releasing updates for my TV about a year after I bought it, but security vulnerabilities were still being found.
Maybe my hardware is just on the older side—it’s a whole 5 years old now!—but Samsung TV apps are pretty slow compared to apps on third-party hardware and always have been. For example, my Samsung TV natively supports Miracast, but the latency is terrible compared to an external Microsoft Wireless Display dongle.
Here’s what I use for everything you’ve mentioned, no phone required, although it might be overkill for casual use:
Plex: Apple TV
Steam Link: Steam Link (although I should probably stop using that deprecated device and just use the app on Apple TV). I tend to favor Parsec over Steam Link, though; it’s less convenient but has lower latency and isn’t limited to games. I also have a Microsoft Wireless Display dongle, which is generally the most convenient of the three and still has low enough latency for casual use, although I wouldn’t use it for gaming.
Retro: RetroPie
I know it’s inconvenient to have additional devices for all of these when you could just use the apps on your TV. Strong passwords are also inconvenient. But is it worth getting hacked or dealing with Samsung’s problematic updates? Maybe someday the situation will improve, but until then, either choose a different brand or use external devices.