Having already configured a VLC-powered Google TV configuration with USB hard drives for a relative without the router or download speed needed for reliable streaming, I'm now trying to configure a similar setup for another relative with a non-smart TV and an even slower download speed.
The only requirements for such a device would be the ability to be controlled entirely with a remote, a USB-A or USB-C port compatible with USB hubs and media storage devices, and the reliable playback of videos of assorted codecs and file extensions. As Roku, FireTV, and Android/Google TV streaming sticks tend to be plastered with ads as a means of promoting content within their ecosystems, an alternative HDMI device that minimizes the number of button presses between turning on the TV and and reaching the navigation menu for videos on attached USB storage devices would be preferred.
I have a Roku (apart from a static ad on the home screen, I haven't noticed any problem with them and if it was really an issue I could use adblocking DNS servers), and can play media on it from a NAS drive, or I can plug a USB drive into my router and access it that way. It's all controllable via the remote and provided there's good WiFi signal, doesn't require a fast internet connection. Saying all that, I do have fast internet and usually just stream stuff to it via my phone/tablet and the video caster app.
I can imagine the phone-to-roku streaming method working well, particularly given the simplicity of Roku OS, though in terms of USB drive usage, past testing on a dedicated Roku TV has been mixed in terms of codec compatibility, unfortunately.