> Why aren’t there more ‘semi dumb’ Ethernet or wifi products that just let you announce that dinner is ready?

Because of 2 reasons

1) this is very antisocial behavior.

2) so many people have a mobile phone at arm's reach a majority of the time so there you have your intercom.

Well educated members of an household would know when dinner is ready because they would actually help make it ready for everyone. Occasionally one teenager could legitimately focus on homework but it is not actually a bad thing that someone has to move its ass and walk upstairs to knock at their door and tell them. We call that free exercise, much cheaper than a fitness subscription.

When I hear about home assistant and domotic in general, the only image that comes to me is those scenes in Wall-E where people live in a flying armchair with a holo screen in front of their face 24/7, their only interaction with a physical world being to only move their arms once in a while to grab a soda.

When I was a kid I remember a house we rented for a while came with intercom using the electrical lines. Past the initial novelty, they mostly collected dust and ended up being unplugged.