Though I agree and sympathize with your "pause dimming/obscuring frustration", you are wasting your time taking this issue to Roku, as indeed it is the channel/app providers that control their channel/app functionality.
That being said, the prolonged dimming/graying coupled with screen obscuring during pause probably comes from a couple of modes of thought by the developers:
1) Pause obviousness (users know its in pause mode, because the video is obscured in the background and the playback controls are emphasized and show in the foreground).
2) Screen/display protection (to prevent/limit "bern in" and "image retention", the screen is dimmed/obscured to prevent these/make them less likely to happen from a prolonged pause, assuming no screensaver).
Many streaming device channels/app/services seem to subscribe to these "pause principles" and its become pervasive across their apps/services on all platforms, not just Roku.
The solution to this would be an user-configurable app setting "dim/obscure on pause" that is enabled by default (that can otherwise be disabled), however, most service/app developers arent really interested much in the UX (User Experience) as much as they are pushing/maximizing content availability and usage (as evidence by this and many other non-user-friendly UX default non-alterable settings).
(NOTE: Why is the word "b u r n" banned?: "The message body contains b u r n, which is not permitted in this community. Please remove this content before sending your post.")