As a techie and a possible user, I agree that I'd like that feature.

As someone who has/might work for companies building things like that, it sounds like a nightmare. It's a ton of design, testing, translation, validation, etc work to build the UI for adjusting optional settings. And it has to be maintained and tested through all future versions, redesigns, refactorings, etc. It's gonna be a tough sell to do it right considering:

For every 1 techie who legitimately uses it to set it to his custom server and can handle debugging when it goes wrong, 50 people will accidentally set it to something random, or have some distant relative set up some weird hack and then disappear when it breaks, and then call the support line and rage at somebody when it doesn't work and they don't understand why, and rage some more when they can't get the instructions to reset it right.

Whatever feature somebody else is about to propose to fix that is yet another thing that will need design, validation, maintenance, etc forever. It's pretty understandable why product designers would rather build simple dumb UIs with no options that mostly work automatically.

The point is I wouldn't have to change my DNS if they didn't inject adverts into my homepage. When I bought the TV there was no mention of Adverts included.

Amazon sold two versions of their kindle, one with and one without ads, not an issue for me. As customer the pro/con relationship is clear. I get what I pay for.

These ads slow down my TV, waste electricity, waste my time more importantly. It's not my problem as a customer if other people mis-configure their TV and have to call support, that's a UX problem, I've never met anyone who has mis-configured their DNS on their phone. If you've updated your DNS on your TV before it's a very long process, using arrow keys to select characters, it's not something you accidentally do.

I paid for a TV and I didn't get what was advertised. The argument that they do it to protect dumb users is non-sense because the TVs that don't have this configurable in the settings are the ones mainly bundled with ads.

Most important, TV ads also may show scary or sexually suggestive material to my young children because the TV doesn't know how or when to be more discreet.

So as a techie I agree with you but as a user I don’t really think it matters. If your device exists to connect to public endpoints and uses mDNS for local discovery then any public DNS server should be fine. All these devices want is a clean connection to the public internet and you’ll never see them officially supporting blocking. At best DNS filtering is a hack that currently works because most people don’t do it and there’s little pressure to work around it. The device is free to exfiltrate all your private data through the connection to the manufacturer’s servers. It doesn’t really need DNS to do it.

I bought the device to stream content not to display ads. So you'd be happy if every laptop manufacturer installed crypto-miners on a new laptop you purchased without telling you before purchasing the device with no way to remove it. It's no different than ads, they are using your resources without your explicit permission after the sale of the device to generate income for their company.

It's madness to me that people find this acceptable. These companies are profiting off the ignorance of people and misleading customers on what they're actually selling them.