Much of what needs to be said is said here. I'll just offer a few other points...
OP is right in that many competitors have caught up or passed

TV in various ways. Apple was somewhat the immediate leader when the first generation box rolled out. It had many innovations in one box. Remember how we used to store a library of music (CD changers), a library of movies (DVD changers), photos (paper photo albums), home movies (VHS tapes or DVD discs), etc. Before

TV1 how did the masses get a podcast/vodcast playing on their TV? Internet radio playing through the best sound system in the house? How did we rent a movie that didn't involve driving a car to a video rental store? Etc.
It was one big hop forward. And then...? Apple shifted it into hobby mode.
Meanwhile, other players looked at all of that innovation and started up their copying machines. Apple got competitors making

TV-like boxes and showed TV and cable/satt box manufacturers other kinds of content/apps to try to weave into their offerings. And they did.
When they generally caught up to

TV, they had to innovate forward and some of them did too. And that can make even the "4" seem like it's more of the same rather than something that might be called "the future."
What's needed here? Focus. Apple needs to bring hard focus on making the "5" leap ahead of the pack. For example, what does Roku most tangibly offer that

TV lacks? Roku has long since and is way ahead on content deals. Is Roku richer than Apple and thus able to buy many more such deals? No. Does Roku have more human resources to forge such deals than Apple? No. So how does Roku do it? They have much more focus on this kind of product than Apple.
To OP's "what's the point?" question, I think it currently comes down to just a few things:
- how much iTunes DRM'd content does one own? If it's much, the ONLY way to easily play it on home AV equipment is through Apple hardware like
TV. Comcast X1, Dish, etc can't play iTunes DRM content
- how many TVs does one have in a home? X1, Dish, etc require leased rental boxes hooked to each TV. Those leases can add up. If an
TV can deliver much of the same to alternate TVs, it will be cheaper to use
TVs over time.
- what does the
TV do that X1, Dish, etc boxes can't do? This is probably a small handful of iOS-specific (proprietary) features that Apple won't share with X1, Dish, etc. Is any of those features important to a potential
TV buyer?
- how into the Apple ecosystem is someone? Buying content through
TV makes it sharable to other Apple hardware without jumping through any hoops. Buying content through non-Apple hardware may require some hoops to get it playing on iDevices or Macs. Etc.
There's probably a few more points I'm leaving out. Is that an impressive list? Eye of the beholder. Hop back to shortly after

TV1 launched and the list would be much longer. Unfortunately, Apple has somewhat dragged it's feet with this "hobby" for almost too long, giving the copycats time to replicate much of the "what's special" and even add a few things Apple's box does not (yet) have. Again, much of the bigger picture answer comes back to FOCUS. If Apple would go at

TV like it goes at other Apple products, it could probably leap out well ahead.
Personally, I really like

TV and I have Dish and app-capable "smart" TVs too. Both of the latter can run the same, most-used apps that tend to be most used on the

TV, so I could easily make a good case for why we wouldn't need our

TV boxes if pressed. Nevertheless, we like our

TVs vs. the other options. And that might be THE "answer" for many.