I don't wanna hate on IS too much. I did quite like this content and it was a relaxing grind to fully max out my island. In fact I'm still working on getting all the rewards and getting all the rare animals. I will also commend this content for having really solid rewards in general with like 5 mounts, minions, good glam, etc.
However when this content was first announced people got excited because of the idea of an animal crossing/stardew valley type experience within FFXIV.
"Isn't that what island sanctuary basically is?" On the surface level yes, however what IS is missing is the endless repeatability that causes those games to rack up such long play times.
The content currently is this: max out your structures and then do the workshop every week. So the problem is that maxing out your island feels like "completing" the content, even before you get all the rewards which doesn't take too long either. Meanwhile sim games almost never feel "completed" eventually you just stop playing them. I think the workshop was what they were trying to have be that repeatable gameplay loop but I don't think it's a very good system sadly. Without using outside resources it's extremely obtuse and inefficient unless you have an economics degree so everyone just copy pastes their workshop plan from discord, essentially making it braindead content. At that point they might as well have just made it a turn-in system where you are given a list of requests from clients for the week on what island goods they want.
IS was never gonna have nearly the depth of a standalone game like AC or stardew, but with the content still being updated they can still fix this in the future. There's basically two routes to go with: the animal crossing or the stardew approach.
The animal crossing approach: the less likely of the two. AC is so addicting because of the endless pursuit of cosmetically upgrading your village/island and your player home. However they decided not to make IS a personal housing system so this can't really work at this point. This requires a lot of furniture and decoration assets to be made, which would take a lot of work for side content without bringing over the existing housing system that already has these assets and then you'd spend a lot time beautifying your island. However AC also has a major gameplay loop of collecting fish, bugs, and fossils. I think they somewhat achieved this with the rare animals system actually but maybe they could go farther. Maybe an island treasure system could be cool. You also have the gameplay loop of befriending and collecting villagers which I don't really see them doing but hey it's possible with NPCs.