I installed an AppleTV recently, so I don't have much experience. But the first thing I saw after the initial setup was one/third of the display advertising a TV-show on a subscription service I had to purchase. Would that count as an ad?
That’s very different from turning on your TV and seeing an ad for Mercedes or whatever taking up the screen.
They won’t actually let you delete the Apple TV app, but if you move it out of the top row you will never see the ads.
My parents have an Amazon Fire TV and when I go to their house and have to use it it drives me insane. Carousels of adds large at the top, banner ads as you scroll, full rows of sponsored apps. Full screen ads for random Amazon products when you pause any show you are watching. Everything you watch on Amazon’s streaming service has minute long unskippable ads. Sometimes when you turn it on Alexa will just verbally read you ads.
It’s truly a dystopian piece of tech.