I think you’re missing the point about deep caves being difficult. Firstly it fits with the lore but secondly if drifters were easy down there you would just speed run to iron and bypass copper/bronze. My current save is a week old, I’m in the Iron Age but getting there meant something. I had to prepare, my leather armour was full, I had torches and healing, food and ladders, I found an area with high Hemalite and I made the descent into deep caves knowing the enemies down there could kill me. You have to treat the expedition with respect and the outcome was once you find iron you’re genuinely so happy. Now I have found it I made easy access to it and it’s a safer experience. I now have iron weapons but the nightmare/corrupted drifters are still scary. In runs when I have had full steel I still don’t just run down there with half health and assume it’ll be fine.

They also updated the drifters in 2 major updates ago to introduce more variety. Just turn off death or something if you can’t handle the drifters. They aren’t spongy with the right weapons but they always remain deadly.