MTF charts are one aspect to check for lens IQ but there are a lot of other factors which make a lens a good tool, just in the IQ department.
MTF shows resolution and contrast. Yes, there are additional factors for overall IQ, eg. color reproduction, vignetting, which are not directly visible from MFT charts. In practice however, lenses with better MTF values are typically also better in other IQ dimensions as well.
Comparing 2 different Canon lenses based on their Canon-supplied (theoretical, calculated) MTF charts gives a pretty good appreciation which lens is better in the IQ department, even in dimensions not directly included in MTF.
so, RF 24-105 / 4 L IS is NOT significantly better than EF 24-105 L IS Mk. II. Although I wish it were.
