Island Sanctuary is being discontinued?

[RaideDuku]

For me, it's more like they used up all that time and resources to make it and now it's getting just dumped without them trying to make it "better". (ㆆ _ ㆆ)
Iscah's pointing out that the devs don't do multi-expansion spanning content is also something that adds to it too.

Keep putting resources into something in the hopes it'll be good eventually?

That's how you get Diadem. No one wants another Diadem.