I think its mostly due to poor build up.

Shadowbringers while it does an interesting twist in 4.4 into 5.0, it also leaves little room to properly build up the new world. At least with radz-at-han it was more established since 2.0. As its more interested in the cosmic scale of things.

Like lets go with two easy examples by comparison. 2.0 to 2.55 establishes Coerthas, but also Ishgard and all that would come later in 3.0. While 2.0 to 3.55 is more about establishing all that would come with Doma and Ala Mhigo.

Shadowbringers, while it does something different and interesting, its more a mood thing than a world establishing thing in 4.4 to 4.55. As its wants to create tension and mystery and the payoff with 5.0 is a black mirror of the home world. Its also more interested in building up and portraying the whole cosmic scale of things rather than doing more work to properly establish new locations for future expansions, that of radz-at-hand, the new world (aka tural), and meracydia. Which would be fine, if shadowbringers was the penultimate expansion with endwalker being the last expansion the game got. But its not.

That of the three afformentioned future location, at least radz-at-han and meracydia were having build up since 2.0. Tural is more fragmented and had more emphasis on a handful of concepts. Such concepts are: Some food, the city of gold, blue magic and the whalaqee, a two-headed mamool ja leader, and where mamool ja come from.

Which I feel we would have had more proper connections and storylines if frankly 5.0 to 6.0, 6.1 to 6.5, and 7.0 to 7.3 weren't all about other worlds as the home world feels like its shrinking and being overtaken by all this shard stuff. Especially if there is meant to be hypothetically 3 to 4 more expansions of this.