Again, I see the desire to savescum as a symptom more than anything else. If you find yourself reaching for the quickload button, it's because the game didn't make it interesting enough to keep going despite something going wrong.

This is at least the case for choice-based situations, where it's incredibly common for there to be an "optimal route" and for the alternative or failure-state to be much inferior in both rewards and enjoyment.

For games where overcoming a challenge is the primary experience, such a beating a Dark Souls boss, then sure. Being able to quicksave at the start of each phase of a boss would be bad since the point is to overcome the challenge of managing to scrape through the entire fight.