Geoff DannThe 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.
The core difficulty is that we have 2 versions of physics and they are mathematically incompatible, which is why the search for a quantum theory of gravity has failed. Saying QM is the physics of the very small, and GR is the physics of the very large does not solve the problem.The solution is this: instead of trying to force these two kinds of physical together into one continuous model, just accept there are two of them, both of which apply to the whole cosmos, with no small/large distinction.