The reason cosmologists cannot figure out what is wrong with ΛCDM is that the core problem is metaphysical, not empirical. If we take the same empirical data but change the metaphysics from physicalism to a hierarchical information-based neutral monism, every major anomaly in cosmology either dissolves or is fundamentally reframed and made tractable.
@GeoffDann https://doi.org/10.5281/zenodo.19392828
This is a cosmology model I have been working on and publishing openly via "Zenodo". I have full confidence that this Cosmological model does help resolve your observation towards the ΛCDM, the standard model of cosmology. Let me know what you think. I'm always open to feedback..