The reason that content providers are ultimately responsible for an app being produce is that they have access to the inner workings of their systems. LG cannot magically produce an app if it relies on accessing someone else servers, APIs, CGIs etc. As for not being able to display Hotstar's desktop version (I am assuming you are talking about their website) then I am guessing it has some reliance on Adobe Flash on which much has been written on this and many other forums. Flash is outdated technology, it is dying and will be put out of its misery in 2020. No major TV manufacturer to my knowledge supports Flash in their browsers do to the complexity of programming for it and its many security issues. Content providers that still rely on Flash are sadly not moving with the times, even Amazon whom it could be considered forward thinking still have a certain level of integration with it.
If you want an app from a content provider or you want to be able to view their website in the webOS browser then the only people you should be complaining to are the content providers themselves.
That said it would be nice if LG acknowledged that there is a call for specific apps and let the users know that they at the least had reached out to content providers to offer help in developing for the platform.