Most of the complaints are that Roku won't allow users to reprogram them. And some say they'll go buy a Fire TV because of it. Fire TV doesn't have any shortcut buttons, by the way. Meaning that if they can't get four out of four buttons they like, they'll take zero buttons.
One was unhappy that he couldn't be guaranteed that he would get a particular button, so he just wouldn't buy a Roku. Again, see the bit about Fire TV devices not having any buttons.
Some Android/Google TV devices have a Netflix shortcut button, but that's it. Fire TV and Apple TV don't have shortcut buttons. Roku has four, but there's no guarantee what they would be.
Roku sells the buttons to companies. Netflix, Disney+, Apple TV+, Hulu, and others will buy buttons for the device. They'll pay Roku good money to get a shortcut button on the device. And those four I listed are the ones on the Roku remote I use the most. Sling, Vudu, and ESPN+ are on other Roku remotes. The five Roku remotes I use the most have a total of seven different apps. So there's no guarantee of anything.
However, people get really ticked off about them. Another common complaint is that they keep hitting the buttons. Apparently not hitting the buttons is too hard.
I don't understand it. If I don't want to launch Apple TV+, I don't hit the Apple TV+ button. If I don't want to launch Netflix, I don't hit the Netflix button. This ain't rocket surgery.
But, people are different. And they get all bent out of shape about things like that. Rather than high gas prices. But me? I hate high gas prices. But I'm quite capable of not hitting buttons, so there's that. Of all the things going on that are wrong, my Streaming Life is surprisingly calm.