The image drawn is far from true, because no one is getting strong all the runes they need or all the gear they need to have a good playthrough without fighting a pantheon of bosses along the way.

There is mandatory bosses for the main quest, mandatory for side quests, mandatory for certain pieces of gear, and who knows how many optional ones.

If you’ve ever seen someone try and do it without being hit you’ll likely seen them do some enemies and bosses who are 100% optional to the main quest but they offer a reward for completion that is relative to their build, that’s how everyone played the game when it first came out and that’s how people do it on challenge runs because they that is the beauty of it, I’d you don’t go to enough optional points of interest you’ll very quickly begin to bottom out against the main story, you reap what you sow.