I think this is fairly well solved from a mathematics point of view (high-school level k-means clustering). The unsolved bit is simply how we get the Spotify et al. product managers to care.

All they need to do is filter out content with genre=kids from recs. They could create a separate kids recommendation item if people actually want that.

This wont happen whilst they have family and kids’ account types. Charge parents more for the premium option of not filling their carefully curated genre recommendations with nursery rhymes and Ed Sheeran.

It's fairly trivial to keep the recommendations consistent depending on the latest request, not just the logged user. Pandora does a good job at this. We have it on our Alexa and at dinner, we take turns with the kids requesting songs. If we stop requesting, it keeps playing an internally consistent series based on the latest song we asked for. So if it's the kids' choice, it's a never ending row of Kids Learning Tube :-)

Spotify is missing user profiles, in the Netflix fashion.

From a technical point yes, but profiles are too rough and hard to use for this. What I mean is more some way to automatically maintain a kind of sub-profile, for each different aspect of a user, but exposed user-friendly and effortless. Most people won't maintain a separate user profile just for recommendations, as it's too much work for too little benefit.

spotify is usually on people's personal device like a phone not on communal device at home like a TV.

Speak for yourself. I use Spotify on my TV at home. Multiple people use it.

rude response.

i said 'usually' .

I would consider Alexa a communal device. Spotify is heavily used there in households. Source: worked on Alexa.

It should be noted that in a Tesla, changing the Driver Profile (stores settings like seat and mirror positions) also changes the logged in Spotify account.

For young kids with no personal devices of their own, they would only get Spotify from their parents' devices.

People use it to play white noise for their babies which makes all the future song recommendations useless