I don't think there is anything wrong with fetch quests. You could reduce almost every adventure game puzzle down to a "fetch quest" if you wanted. It's the story around them which matters.
Asterion is a great example. I'm presumably going to find him dead at some point, then return to the starting location and get his items. The "fetch quest" isn't even an item, it's a piece of information which I'll "pick up" automatically.
However, the quest doesn't just send me over the other side of the map and back again with nothing in between. There's a whole storyline and mystery about it, the relationship between Asterion and other NPCs to explore, it's actually very exciting.
You actually do have a single-item fetch quest in the berries for the innkeeper, but if you talk to the guards then you'll learn this is a basic test to make sure you're trustworthy. The quest isn't about fetching berries, it's about proving that you're reliable and humble to another NPC. That's a lot of extra stuff added to a simple basket of fruit!
I trust you'll add a compelling story around most long puzzles. You seem very good at writing these intertwining storylines that make solving puzzles very rewarding to the reader.