I've been playing for a while and sadly I stand pretty firmly on this - the worldgen kind of sucks, ESPECIALLY if you want to travel long distances by land.
The terrain is just way too rough in way too many places. I wouldn't mind a kind of biome/landform that generated as those jutting pieces with 20-30 block deep holes between them if it was a rare occurance to spice things up, but from my experience it's as common if not more common than plains or gentler hilly terrain. It's just not fun to traverse in my opinion, on foot nor on elk, and it's not easily ridden around because it's surrounded by water, mountain ranges or just more of the jutting rocks.
Mountains are not great either, but I like to view them more as an obstacle to ride around rather than through unless I manage to find an interesting and not painful-looking lower passage I can take.
I'm not a fan of the floating pieces and the jutting rounded rock formations that look like the worldgen just repeated parts a few times upwards, but that's more aesthetics than anything else, I just ride around them like I would with normal mountains.
Changing worldgen options didn't really help me either. I tried vanilla and Plains and Valleys, Fields and Plateous, both of the mods combined as well. What I want to get is way more flat plains with occasional mountain here and there, but even when I lower the Upheaval Rate to 10%, the mountains are everywhere. Landform Scale setting is hit or miss because it lumps all the landforms together and changing it for under 100% gives me thinner valleys betweens those mountains that are everywhere which is worse. Changing it to 180% as I tried the most made plains bigger, but it feels like it makes mountains three times wider than them in turn. I just can't seem to fins a way to have giant rolling plains with thinner, rarer mountain ranges no matter what I do. It's all mountain, all the time.
I really hope the worldgen improves in nearer updates, even though in my opinion it should be tackled before adding story locations and transportation options or it makes those a moot point, tho that's mainly just my opinion. What I hope the most of is to see a realistic terrain generation mod similar to Terraforged I used in Minecraft, with similar amount of customization. That would make this game truly the cream of the crop for me since I loved almost all of it, just not the terrain.
That being said, I might just be making some mistakes with customizing worldgen. What settings do you all use and would you have screenshots as examples of results? I'd love to experiment, both with vanilla and the above mentioned mods!
EDIT: I tend to go for 384block tall worlds. I might not want mountains everywhere, but I like them tall when they are there! Don't know if that would affect anything else in worldgen.