I might pay $350 for a phone that does only what I need, but I'm definitely not going to pay $350 extra for a second phone that only does what I need on top of a modern smartphone to leave at home that does lots of crap I don't.
The second Light Phone looks like it started moving towards being feasible as an only phone, but also piling on a strange set of features, for a phone designed to limit distractions. There's still SMS messaging but no encrypted messaging or email (and they brag it will never have these), but there is now music and ride hailing and so on.
So close, and yet so far! Any telco entrepreneurs out there: make me a little box that's only about communication with individuals I know (talk, text, popular encrypted chat, email), with modern interfaces (LTE, Wifi, USB-C), and I'll buy one. I bet my parents would, too.
$350 is not the problem -- service will still be the biggest cost in the long run. It's just not a useful device even for people looking to slim down and avoid distractions.