I’m no PoE expert but in my experience (played 6 weeks heavily on scourge league and went through most of the content), DPS in very important in that game, you want to keep momentum going so your flasks and buffs have full uptime, also many bosses have DPS check-like mechanics, plus so many normal/rare monsters may have cheap strong attacks, the best answer is to erase them before they can even attack. And so many league mechanics are on timers or build up as time goes, the faster you clear, the better you perform. Also defenses/immunities are very important, but DPS and speed take priority.
In last epoch you can clear most of the game with hit damage (example) doing fast 20k attacks, or fast 100k attacks, clearing mobs won’t make much of a difference in say, 200 corruption, you will notice with beefy elite and rare mobs, but the experience stays mostly the same. Bosses have a DR system the more damage you dish out quickly, more DR they stack, so, while you still clear faster with high DPS, you are soft-discouraged to build high DPS to try to skip boss mechanics. Many skills do build up, but usually build up and wear off quickly, you don’t need to keep de buffs from pack to pack, more DPS is always better, and feels better, but you don’t have a game that screams you to get more DPS in every way possible.
On the other side, what keeps you from going higher corruptions to farm items with better quantity drops, are defenses. Once you get the basics sorted (a healthy HP/ward pool, crit avoid, block/glancing, etc), you will push up for better armor, more HP, better Endurance, more evasion, armour, you will cut from offense to get more defenses in passives, and sometimes skills. You will optimize suffixes with blessings, and better bases, so you can fit in more HP suffixes and idols, you will double/check any source of DR, etc. This is because in monos, while you push corruption past 250-300, you start seeing mods like “enemies have 150% increased elemental/void/physical damage”, and those go through the roof as you climb corruption, if you can’t manage a few offensive mods, your experience will be miserable.