In the words of the late Steve Jobs - the Apple TV is a hobby.
Tim Cook said six years ago that he would stop referring the Apple TV as a hobby after the Apple TV made Apple over a billion dollar revenue from ATV sales, and iTunes sales and rentals.
With the launch of the tvOS, that was suppose to be a new beginning for the Apple TV. The rumors leading up the the Apple TV 4 (HD) showed that Apple wanted the tvOS and the Apple TV to be something big.
But, what Apple delivered in 2015 wasn't what was rumored, and while a lot of the issues were corrected over the years, and with the A10X in the ATV4K, it appears that Apple is now treating the ATV as a hobby again.
App developers have been lazy on this platform, other than a few gaming developers, no one seems to be bothered.
I think you are right, but it isn't like developers have tried in the past, and when tvOS first launched, Apple made it very unfriendly towards developers.
With the horrible 200MB limit for static storage, and the Siri Remote requirement, these two things alone probably deterred the majority of AAA developers. The (relatively) slow A8 instead of the A9X also probably played a factor in making developers reluctant to dedicate resources to tvOS.
Even though Apple has since walked back these ridiculous requirements and the ATV4K had the A10X, I think the damaged was done.
The few developers that manage to work around the missteps that Apple made in the beginning are now starting to abandon tvOS. Many apps on tvOS are no longer working, no longer being updated, or just pulled from the tvOS App Store, while their iOS counterparts are still getting updates.
I don't blame them, as why should they care about developing for the tvOS when Apple doesn't seem to care about it.