A good tradesman never blames his tools.....yet you see it so often on this (and many other) group(s).
I suspect much of the problems stem from not understanding the limitations of the tools at hand. Yet a true artisan can make an artwork from nothing more that a sharp saw, chisel & hand-plane.
Take RGB filters. Provided they have the same thickness they will indeed be parfocal. But drop a refractive element in front of them, and I can almost guarantee you will have different Red, Green and Blue focal points.
Similarly with 1:1:1 exposure times across the RGB spectrum. It is an elementary procedure to have a look at the QE curve of various sensors and discover they are very unlikely to be equally sensitive across the RGB spectrum. To allow "leakage" from R to G or G to B for the sake of a 1:1:1 exposure makes it difficult to get accurate, saturated colours IMHO.
Much can be learned from imaging a photographic colour card in daylight with a CCD and various filter sets to discover what exposure ratios are required etc. (I still use unfashionable, bog standard CS filters
)
In any event, with whatever equipment choices you make, selection of the right tool for the job/problem at hand will save much subsequent image processing grief !