> The whole point of mirrorless was to move away from DSLR sized kits

That's a wrong assumption, it was certainly never "the whole point", just one of the factors.

Besides mirror slap/vibrations, what's the other benefit? Size, and therefore cost, of glass is why all of my professional friends moved over. You can get better lenses for cheaper. And, the cameras themselves are much simpler, so can be cheaper/higher quality.

Many of the "live viewfinder" benefits already existing in DSLRs that had live viewfinder modes, with the rest being excluded for cost or differentiation (focus pixels, live histograms, etc). I saw it as an more of an eventuality of the live viewfinder being made more featureful than the lens view, so removing the mirror just made sense. The only people I know that are still using DSLR are those that "need" the classic viewfinder, but there's no reason the features of a mirrorless camera couldn't be put behind a sometimes-flopping mirror. The only problem with that would be vibration and the increase in size of the camera and lens.

The lower back focal distance from not needing a mirror and optical viewfinder allows significantly better optics.

> allows significantly better optics

Yes, that's the primary driver for the size/cost of an equivalent lens. Smaller lens also means less distortion/non idealities, for the same cost.

Distortion is cheap to fix in post.

Field curvature, astigmatism, coma, and chromatic aberration need to be handled optically. A larger sensor remains beneficial, even if the lens is physically larger, at least as long as you keep a wide aperture.

There is a hard limit at F/0.5 that you won't get closer to than ~ F/0.65, but the crop factor makes it so you have a smaller absolute aperture with a smaller sensor to get the same field-of-view.

MFT needs half the focal length and half the F-number to match full frame in FOV and DOF. E.g. an F/1.3 full-frame lens already matches what exotic optics can reach on MFT, and an F/1.0 one would match the theoretical limit of MFT.

Speaking about more realistic MFT lenses like F/1.4, that'd be a rather harmless F/2.8 in full-frame. Yes, the latter is more expensive, but only because F/1.4 is quite a bit away from F/0.7, the practical limit for "normal" photography lenses (anything faster is probably exotic).

All of the initial mirrorless cameras were substantially smaller than the DSLR equivalents.

Not sure what other benefits mirrorless brings.