Since when is jumping in a Witcher style RPG important? I never heard to complaint about let's say Neverwinter Nights or Dragon Age (both games feature the same over-the-shoulder perspective used in The Witcher). Now I do agree that not being able to jump in Risen or Oblivion (or games such as those - i.e. directly controlled, very open games) would be bloody annoying. But in other RPGs? I honestly don't care.
And yes, not being able to jump in Guild Wars was annoying.
Obviously, it's important if you like the freedom of movement and the ability to go where you want to go. It's pretty frustrating that you have to go all the way around a tiny obstacle and spend 5 minutes running, when you could have just climbed for a second and been there in a fraction of the time. No one would do that in real life - and since I'm rather impatient, it bothers me that I have to waste so much time doing things that I would never do if I had the choice.
The Witcher struck me as a relatively open game once I got to the first chapter, and I was pretty annoyed at having to follow linear and rigid paths around the landscape.
But, it's not a huge problem. It's an annoyance that didn't really have to be there.
It's a matter of personal taste, and obviously - you didn't have a problem with it.
Sometimes, to understand where people are coming from, you have to go beyond yourself and explore what matters to other people.
It must be said, though, that I'm a great fan of freeform and open world CRPGs - and it's true that The Witcher wasn't about that. Also, I think it was more about the engine than anything else.
I understand if you're attached to the game, and you consider it a great game - it can seem like nitpicking. But I think it's key to understand that we don't all think it's a great game - and sometimes even the greatest games have flaws that may be significant.
All my favorite games have significant flaws, including System Shock. It wouldn't sit well with me to call people nitpickers for pointing them out - regardless of how I personally feel about the game.
It doesn't have to be wrong when people don't like something you enjoy or don't mind.