The whole concept of decentralized trust-less environments requires some way to prevent malicious attackers from taking over the network. Proof of work, while extremely wasteful, does that job.

The main problem is that trust-lessness and decentralization isn't actually necessary, especially for most things that exist in the real world and are at the mercy of the legal systems they operate within (this applies to cryptocurrencies as well - the government doesn't need to break crypto, it can just make interacting/transacting with it illegal).

For a lot of real-world projects, the legal system is an adequate protection. Centralization doesn't require a profit motive - the central party could be set up as a non-profit and then have all the advantages of a centralized system while avoiding a lot of the drawbacks we see in for-profit operations.