Profanity: If you've died - there's a problem, you fucked up somewhere and that's one of the fun parts, it has consequences. A lot of games lost that and are becoming duller and duller in comparison. DaS/DeS are less forgiving than what we have these days after all. If you can't clear something in here, means you'll have even a more bitch of a time later on and we're not letting you get there until you prove that you're good enough.
This is the same mentality most games have stopped following. You usually no longer have to prove anything, any challenge to a game becomes just sitting there the 10-25 hours the game requires you to. You've been on GOG since 2008, I'm sure you've played your fair share of old games, I think you get this.
Not to mention, if you think that you didn't fuck up and think that you don't have to clear this little area again just to get to the boss - run. You can run over any mobs in the zones and just get straight to the boss. You're not required to bash everyone's head in again.
We've got it too easy, visual novel games with WASD controls are the new wave.
Inclusion of saving != easy game. The game is just as difficult with saving as it is without saving, it just adds a lot of repetition, which is what I can't stand. For example, Devil May Cry 3 - quite a challenging hack and slash, and I have finished it on highest difficulty. So what is the difference between repeating the same section in Dark Souls and in DMC, you ask? Well, Dark Souls is an RPG. As such, when you pick a character, you get a optimal way to play the game, and Dark Souls is one of those games which will punish you for not playing optimally.
Now, why am I bringing this up: When I have died in DMC, it was always because I have fucked up. Every single time. That game could be beaten without getting hit a single time if you have superhuman reflexes. However, when I've had to repeat a section, I could vary things up: Grab different weapons, different combat style, and various combos just kept things interesting.
Not so in Dark Souls. In Dark Souls, you profile your character to be good in specific areas, and specialize on specific equipment. This basically means that when you fuck up, you have to repeat the previous stages precisely as you played them before. When a game is structured like this, I want the ability to just skip right to the bit I have fucked up at so I can find out what I did wrong and fix it - repeating precisely what I did before feels like an unnecessary waste of my time. It just feels tedious, I have been there, I have done precisely that, it's not very entertaining to do it again.
Now we're at the saving vs difficulty bit: You can actually have a game which is difficult and lets you save anywhere. Ideally, and I'm really glad that is the standard nowadays, a game has a combination of checkpoints and manual saving. Some games, like Dishonored, I just don't use quicksaves and rely on autosaves. Others, where I find repetition to be tedious, I use quicksaves. What I dislike is when game designers take this decision away from me.
edit: Now, keep in mind I don't actually want Dark Souls to be different. A lot of people enjoy it for what it is and that's fine.