I switched away from Roku to an Nvidia Shield (an Android TV device) precisely because of the Roku HBO Max thing. Maybe these smaller players don't have the sheer number of captive eyeballs needed to demand such commissions. Although I guess HBO would still have the Play Store fees? In any case, I haven't noticed this sort of customer-hurting hard negotiations yet.
As long as you can watch something on the web, you can always cast it, right? (I find Chromecast is an underappreciated device from Google. I basically never touch any of the smartTV features on my TV. I do everything from phone, tablet, or Chromebook.)
Google hasn't evolved Chromecast past a cheap, dumb dongle since it was first released. No telling what the future holds but the current trajectory is promising.