no, there might be a few large pools though, but i think many use P2Pool also

It's a smaller project than Bitcoin. So there are fewer devs, which makes development more centralized. While mining is more decentralized, hash rate is much lower and it's a big concern. There is not enough hash to protect against a well-funded adversary. Not exactly centralization, but worth no...

Kind of a broad question and depends what you are looking at and comparing to. For a few examples Monero is more decentralized when it comes to mining and mining pools (anyone can mine no special hardware required, and p2pool exists), but more centralized when it comes to node count and contributors...