Voting power concentration is is a highly valid concern, and i’d encourage you all to join the discourse here Request for Comment - Governance Improvement Grants - #16 by mgg as we discuss some potential improvements.
My personal take is that VP concentration is a growing pain, and something that will diminish over time given the progressive decentralization we have seen in the protocol, both by plan, and reinforced by the community. I think we will see this concern go away with increasing initiatives in the realm of monitoring and incentives; something that is being developed in the most recent DGP batch (Grants October '23 Update).