[Klaus]

@Klaus, the wording "ergonomics" is not exactly right; I think a better wording would be "total package size" (TPS).
I don't fully agree that only MFT qualifies here.
If you pick certain use-cases/lens combos, other systems are as well suited, if not better.

For instance, the following setups can be very interesting in term of TPS:

Fuji
- Body: X-T30
- Lenses: 16 f2.8 (or 14), 23 f2, 35 f2, 50 f2
Also the 15-45 zoom is very small (although plastic-fantastic and electric zoom - which I hate).

Sony FE
- Body: A7 III
- Lenses: Samyang 18 f2.8, 24 f2.8, 35 f2.8, 45 f1.8, 75 f1.8
Also, the Tamron 17-28 f2.8 and 70-180 f2.8 are quite compact

Actually I do think that ergonomics is the right word.

A tiny FF mirrorless with 24-70mm f/2.8 simply doesn't handle well because it's so unbalanced. 
This changes a bit when adding a vertical grip - but then the TPS is getting even worse than that of a naked DSLR.

Of course, there are setups where this isn't an issue as you mentioned. Most FF mirrorless cameras are targeting prosumers - and this group tends to invest in such high-speed zoom lenses.