"The ability to navigate directly to specific channels and programs with URIs and customize the interface to suit individual preferences would make using Roku more intuitive and enjoyable for everyone."
You can already do this:
https://developer.roku.com/docs/developer-program/discovery/implementing-deep-linking.md
As far as larger fonts, dark/light themes, etc.. Those are up to channel developers to create. Apps have options to increate text size, use different colors, etc. If Roku were to stick their thumb on top it would make the experience worse. Not better.
For seniors and those with restricted vision, the plethora of apps without consistent interfaces is incredibly frustrating. I would MUCH prefer to be all to 'train' Roku so that, when I want a channel, the login credentials are sorted and the preferred page is available (say a watch list). Getting out of that channel should be controlled by Roku since many allow a simple exit but others moan with "are you really leaving us.." or some such childish behaviour. I'm about to choose a Roku TV for my 94-y-o mother-in-law and she simply cannot see all the pop-up stuff. I chose Roku since I am reasonably certain updates will be applied as opposed to some manufacturers who abandon their products.
