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Intuitive Explanation for why more negative charge on ligand does not imply more splitting effect?

I have studied coordination chemistry as part of my school curriculum and we covered Crystal Field Theory as our final theory, and the book says that Ligand Field Theory and Molecular Orbital Theory are used to explain the limitations of CFT but are beyond our scope of learning.

One of the limitations of CFT according to the book is that if the ligands are point charges then it should follow that an anionic ligand should exert more splitting effect but that is not the case as we see in the spectro-chemical series.

A good example would be $\ce{S^2-}$ < $\ce{F-}$ < $\mathrm{EDTA^{4-}}$ < $\ce{CO}$

Also we can see that size is not the determining factor as then $\mathrm{EDTA^{4-}}$ wouldn’t be so high as compared to $\ce{F-}$

Is there some intuitive explanation or logic for this which I can follow with my current knowledge till CFT without going too deep into MOT or LFT?

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