TV manufacturers' interests are not perfectly aligned with users'. They may want to wow you with the picture, but definitely would like to monetize the heck out of the access to your viewing habits, and the internet connection you might mistakenly allow them to have.

Same applies to basically anything connected to the internet. Can it collect data useful for advertising, or otherwise legally saleable? If so, deny it access to the internet if you value your privacy. Or, when possible, replace its firmware / software with a reputable open-source version.

Follow the money. Can any money be made inconspicuously off you after a sale of the device? Are you happy with the way it would be done? Do some minimal research, and scratch your head.