I think there's a unique issue here.
Fort struck me as a means of solving longstanding issues and 'regrounding' Runescape's story content, whilst Necromancy provided the 'flashy' content.
Necromancy however is a double-edged sword. It's a new combat skill which addressed lots of bug bears (not least new players). But because it is another combat skill, despite being new in many ways and widely used, it is also not-new. And the area that came with it you would not habitually visit. This means that the 'new' stuff in the fort has a lot of weight put on it, perhaps disproportionately so, and feels a bit diminutive.
If I'm honest, I expect this is so unique that there's less to learn from it than may be expected. (Which is not to say that you shouldn't try to learn, obviously.)
However, and I don't mean this in a brow beating way, but I'd suggest the best thing you can actually do, strategically, is announce whatever is coming in the second half of 20...