A few times I've seen or heard of situations with people being ridiculously undergeared for what they're running. Last I got to see myself was a healer in Cutter's Cry wearing a cracked shepherd's belt, which is simply a mat used by crafters to turn into... a vintage gatherer's belt. So no stats at all. He was also wearing a vit necklace. Funny enough the tank was getting hasty and asked if he could do big pulls, and that healer said that he could heal anything with no problem. Turns out he couldn't.

Like that there are many other stories that happen with ridiculously undergeared players, or people who have no idea what they're wearing. They may not be that common, but they still happen. And with such a lack of knowledge or care about their gear I don't expect them to be good enough players to make up for that disadvantage. I don't expect such a stiff limit in gear, maybe to use gear that is at least competent for the previous 1 or 2 dungeons. Accessories could still have some freedom, but left side should have an expected minimum.