The reason these devices are cheap/affordable is because of the open source community. The reason the internet has made it to this current state is because of the open source community. If you want the internet to be better and safer you have to roll up your shirt sleeves and contribute in any way you can.
I suspect the consumer protection laws take similar views in many countries.
Like I said before, there are a number of available DHCP and DNS implementations in memory-safe languages. Many of them are open source. So the vendors don't even have that excuse.
DHCP: isc-dhcp or dnsmasq
DNS recursor: dnsmasq, unbound, bind, djb's dnscache, maradns
None of these are written in memory safe languages, but they're the only ones I would trust because they have YEARS of testing and getting the RFCs right.