I am a strong believer in the right to privacy (even if some people take it what I believe to be too far), and a centralized mixer has the potential to enhance privacy. Also, however, mixers have the potential to give nothing more than the illusion of privacy and highlight your transactions to governments and other nosy people. ChipMixer being the exception (which was shut down by the government), I understand that all mixers have leaked the connections between all inputs and all outputs through their service via the blockchain -- all that is needed to make these connections is a small transaction through their service, or a series of transactions through their service.

The underlying root cause of the policy change appears to be the fact that mixers are getting seized/shut down by governments with increasing frequency, along with the risk that users (and participants of signature advertising campaigns) will be subjected to government sanctions if they attempt to cash out any coin received from mixers.

As bitcon becomes more mainstream, using it will become incrementally less private. There will be a balancing act between privacy, and the benefits of seeing an increased number of people using bitcoin (and layer 2 solutions, such as LN).

For the above reasons, although disappointing, I tend to agree with the decision by theymos.