This is what I do, I'm a little confused by the issue. If you have a device that outputs HDMI just never connect the TV to your wifi. It's not like you need or want firmware updates if there's no internet connection.

A much more fair retort is that an extra device to output video costs more, though I might argue that if you don't use the TV's built in system the manufacturer is losing ad revenue. So if you only use it as a normal TV you kinda are buying it subsidized by everyone else watching ads on theirs.