Things wrong with nomads:
1. Always empires. Not only does this make it so conquering the steppe is less noteworthy, it also made each nomad realm it's own island. I'm not sure if nomad emperor titles are as prestigious as normal ones, but I'm assuming they are. Which makes no sense. I think they did this to make sure nomads couldn't be conquered, which in itself makes little sense, and it's a lazy solution.
2. No inter-clan-itude. Goal of a Nomad realm: Seek and Destroy all other nomads, apparently. Nomad clans should have been able to move between realms. Sure, you shouldn't receive every single clan whose territory you conquer. But you should at least end up absorbing some clans along the way. Genghis didn't become Genghis by fighting every single Mongol and Turk on the steppe. He became Genghis by uniting his allies under hims own banner.
Related to this (and to #1) is that there's also no way for clans to come under the away of feudal lords. I don't know if there's any good record of that happening during this time period, historically, but it's something that seems like it should be possible.
4. Theres no fluid conquering of urban (any settled) counties. The mechanic of how once you have a nomad capital holding in a county you cannot turn it back into an urban-ruled county. Want to conquer Persia and keep Persia around? Nope, sorry. Every county you occupied has a nomad holding in them now.
And that brings us to as how the mechanics are now, you can't settle your own relatives as landed lords of the urban areas you conquer. I'm sure many of you have played at least one game as Genghis at the "Genghis rolls into Persia" start date. If so, you know what a ridiculously humongously sized family he has. Start after he conquers Persia, and you see his sons and grandsons as lords all over the place. But if you conquer Persia yourself, you can't do that. The game doesn't let you put people in charge counties. You can't make your useless second-to-twelfth sons landed dukes and kings. And this is a game about building your dynasty. But Nomads can't do that. Your dynasty only ever has one ruler, and that's you. And that just sucks.
It's the same for non-relatives, of course. But I think that since it's a dynasty game, relatives are bit higher on the priority list to most players. But I can say that long ago, when the Horse Lords was first released, it did let you turn people into feudal lords. Back then I used give out duchies and kingdoms to courtiers I felt had done me great services. Like Subutai.
And that's all I can rant about off the top of my head. I'm sure if I started playing as Nomads again more things would come to my memory. I don't feel their mechanics was satisfying at all. Basically the only things I feel were good about them was the feeling of their armies facing the levies of the feudals.