Primarily because they have to develop a game from scratch and still develop under the assumption this will be most folks' first Souls title.
The PvE is going to be the exact same as Demon's Souls and Dark Souls pretty much, unless you intentionally go out of your way to make it harder, which the game fully allows you to do as listed below. It's new, it's refreshing, but let's be honest, for most bosses if you were a Souls veteran you can kill most bosses while dying only 2 or 3 times prior figuring out the attack patterns and 'rules' of the bossfight.
The PvP is faster though. No more reliance on dead-angle glitches at high level play to counter turtling (hitting people at 90 degrees while unlocked so the game ignores their shield using scythes or greatswords mainly) and kick was replaced with a guard break which takes more timing to use but is far more effective unless you're hitting a greatshield.
Dual wielding actually is viable now, sorcery is /very/ viable now without being stuck using only Abyss magic, and it ends up being the purest of fighting games in a sense. Mushpot builds are viable now as well, so you aren't stuck with only one type of magic if you spec for the appropriate damage type and scaling.
Poise has been reworked so that it's useful, mainly allowing you to recover from most actions faster or being knocked over rather than letting you ignore hits. This does let things like rapier and dagger users poke you to death but that's much easier to fix with proper distancing and timing unlike poise backstab fishing, whose only real counter was abusing Dark Bead or Pursuers.
More damage and spell types were added, more weapon classes were added, and Resistance got switched to a stat that helps determine how many i-frames you get while rolling called Adaptability, it also adds HP and helps with inherent poise which is now slightly inherent, it still mostly comes from armor. Adaptability is basically the Darkwood Grain Ring stat, it scales now. You can still roll without it, but you can't roll 'through' attacks without much ADP, you have to use it solely for mobility. As long as you're not fatrolling, this still works since most armor is lighter.
No relying on RNG unless you wear engraved gauntlets to crit at 5%, and your build can be re-specced with certain restrictions. Exploring the game fully the first playthrough lets you do this 3 times which is more than enough for a typical RPG player. After all that, it's all skill and exploring the environment. People who liked trapper thieves would love the Rat Covenant which lets you set up traps and force players to invade you on your turf... where all the mobs are aggro to them and not you.
You can do Galadon Arena style PvP or go all out murderer as usual and a few covenants in between.
Edited 1 time(s). Last edit at 04/29/2014 05:20PM by Scrimbul.