There is a variety of content, the variety of the content is not the problem, it is the lack of repeatability of the content that is the issue. It's a once and done thing, then maybe you go back for daily or weekly duties, e.g., roulettes, or Island Sanctuary workshop. Longstanding casual players actually have very little to actively do.
Now let's get on the boredom comment.. This is just as much of an issue as anything else you could mention, as boredom stems from multiple areas, inc., lack of repeatability or substance. There is only so long you can do Island Sanctuary for before you come to the stark realization that it is a daily simulator.
Now, nobody expects everything to be interesting, and nor do they expect for that boredom aspect to actually be removed, but they absolutely don't even try to make it interesting or make it repeatable. But hey, look on the bright-side at least the game is getting more bloated visual effects.
