The voting power of DFINITY is derived from everyone who chose to vote the same way DFINITY does. They gain no benefit from doing so as opposed to voting any other way including their own; there is no ‘lock-in’ effect that the word centralization implies. A way in which the people who participate in the NNS behave is being presented as a fault of the NNS; it could not be closer to the opposite, as if you disagree with it, you can participate yourself and stake some ICP behind your disagreement.
To quote the thread you’re referring to (and to link it for discussion participants, as you didn’t):