Morde's new ult is lacking...
...the soul's he ripped off from the prays he killed with ult lurking around in a ghostly form...

...the soul's he ripped off from the prays he killed with ult lurking around in a ghostly form...

What?
I don't understand. Are you upset about Morde's new ult or are you comparing him to Pyke, Karthus, and Yorick? Or both?
For starters, yeah, the Shadow Isles has always been composed of general necromancy, spirits, revenants, that sort of thing. Just like how Ionia is composed of spiritualism, ninjas, warriors, and Noxus is composed of big baddies who like blood and war. It's a region thing, most of the champions from a region tend to share the same qualities.
If you're comparing them from a lore and gameplay standpoint, they're still pretty different.
Yorick speaks to spirits in the hopes of cleansing the Shadow Isles of their curse. Pyke is a revenant from Bilgewater who seeks revenge on all those who (he believes) has wronged him, if anything he's more similar to Kalista than Mordekaiser. Karthus is basically a cult leader who basks in the glory of death and seeks to lure others to the Shadow Isles so they may be exposed as well.
Mordekaiser is using the Shadow Isles as a "base of operations" if you will, to build his army and spread darkness to the rest of Runeterra.
Also have no idea what you're on about fam. NEW ult is 10/10.