As a 68-year-old woman, I don't get to stay at "youth hostels", and my previous experience with a hostel, in Seoul, was mixed. I really liked Sleepzone. It is obviously aimed at the economy-minded traveler, but it is comfortable and very welcoming. All the staff that I encountered were friendly and helpful, and while I don't suppose it's entirely under Sleepzone's control, all the guests were also pleasant and accommodating.
The beds in our room were bunks, with futon-like mattresses on rigid metal grids. They were quite comfortable, imo, but if you need memory foam to sleep well, they may not suit you.
The shower required you to keep pressing a button to keep it running, and very early in the morning it took a while for the hot water to reach our third-floor room. Again, not luxurious, but perfectly usable.
When we got there, our hot water faucet didn't turn off easily; it felt as if it was off while water was still running. Not a real problem, but I reported it the next morning. The desk person thanked me for letting them know, asked if I minded having someone in the room to fix it that day, and the faucet was better when we got back that evening. I've been in fairly expensive hotels that couldn't fix problems in a week.
There's a huge kitchen, with ample table space, and coffee and tea all the time, kept clean and tidy. Breakfast was assorted breads and cereals. Multiple lounges have couches and card tables. It felt amazingly homey.