No, they still have the main game.
And I think there have been releases, just not ones we got access to.
If you look at the patreon, you'll see the island (I think it's got some visual updates) with the combat mechanics used in this beta test.
Basically new things in the game we have yet to play: surfing mech, the new combat system & elements (outside of the realm), free climbing, prettier graphics, swimming system, underwater combat, x-ray scenes, grappling hook (I'm looking forward to this one), new island building, enemy emotion.
Here's some images:
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Here's the kemono link if you want to check it out:
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I highly reccomend checking out the kemono, you really see how much work has been done, still annoying there's no build, I won't lie, but it isn't a case of no work being done. Just that there's a lot of work being done, but nothing released. (possibly because of backlash when they released unpolished builds previously? dunno the exact reason, since there looks to be enough for something playable).
I wouldn't really pay attention to how it's been 4 years (originally wrote 1-2, but damn been a while), because it's an actual game, one where the dev is trying to be really ambitious, which fucks the dev timelines in the ass.
If it was just the island, and only the island, then there'd be pleanty of updates, but you got the zone thing, the dream world, and then the battle mode in the dream world, two of them, and now you're just adding a lot of dev work, but work that doesn't really show much of anything.
Unlike a VN game where most of the work is what players see, games have a lot of coding and background shit you gotta mess with.
Basically, Dev has been developing the game the whole time, just no releases. they just seem to be terrible with estimates (they were trying to release a playable island build november last year)

Game is looking really good, just that we can't play it.
p.s. honestly this build and the whole forbidden space thing, can be it's own game, adds to my point of the dev doing a lot of different things.