I think the complaint about ads is mostly a knee-jerk reaction by certain online communities. The ads are not particularly obnoxious - they are always off to the side and don't interfere in navigation in any way.
Furthermore, I'm on a Roku looking for content and the ads highlight content. It's not that different than seeing posters on the way to a movie theater.
They routinely override the user-defined navigation to include whatever new content they are pushing. It was sold as an appliance without ads or subscription. Now it has become an ads platform that the user has less and less control over.
On my Roku the ads aren't just off to the side. When I go to the home screen there are now "recommended" shows above and below my channels, and they are initially selected, so I have to scroll down past them to get to my actual channels.
Every one of those sections can be trivially turned off in the settings. Mine just have the list of apps I installed on my device.
Yes, which you have to do repeatedly after every software update when they change your settings.