I don't know why people hate nutaku so much. They just lend their servers to other devs/publishers for a part of their earnings. Nutaku can promote the game on social media, their front page, heck, even fake the ranking to attract more people, but after that it's all on the publishers hands to keep their players happy and interested.
To put thing in an example, imagine Nutaku as a shopping mall and the games as stores. If a stores offers shitty/overpriced products, it's not the mall's fault, it's the store's fault. But Nutaku it's not completely blameless.

If a publisher determines that a game it's not profitable anymore and decides to take it down, most of the time (most) it's not Nutaku's fault. Some of the games I played and why I think the closed:
- Aigis: According to the publishers, the game wasn't profitable anymore so they took it down. Nutaku negotiated with them because they knew Aigis was one of their most known games and it's closure would affect their reliability (and it did).
- X-overd: After a few months they had a low playerbase so they weren't getting the amount of money they were expecting.
- Sengoku Providence: The game was killed by the devs from the pre-release because of the greedy management that it had from beginning to end.
- Brave Girls Raven xR: No major updates for over a year, playerbase died out = no profit = closure. What many people wonder it's What took it so long to die?
- Idol Wars: The main mechanic of the game was the PVP. A broken matching system put a casual production against a full-of-whales production, which made PVP a one sided massacre. That scared away many players, and not having anyone to show off your superior wallet made the game boring even for whales.
- Osawari Island: The game was a time bomb since it's closure on DMM.
I don't know about the other games since I didn't play them.