That's true. IMHO, solution to this is not trying to look and feel exactly like native controls, but focusing on providing universally good UI/UX instead. Good UI/UX can be independent of a platform it runs on.

Don't get me wrong, there are a few essential things that you have to mimic in order not to be too alien on a specific platform. But for everything else, try to provide best UI/UX for a specific task rather than trying to mimic some generic controls.

Making a good UI framework from scratch takes considerable amount of resources. The lack of accessibility and localization is usually due to insufficient resources from framework developers, not a technical limitation.