Note that there is also a bit of controversy around flakes. The feature has been implemented without going through the RFC process, lacking input from community. As a result part of the community rejected flakes.
Many also feel that it is a too big monolithic change to the Nix language, parts of which could just as well be implemented outside of Nix (see e.g. niv for managing and pinning sources) and promoting one true way will stifle innovation. Having less controversial features like nix-command and evaluation caching tied to flakes is also considered unfortunate.
However, there is currently a new RFC to try to resolve this situation: