Bad lens, bad image, a larger sensor doesn't help in any way. Good lens, good image, a smaller sensor isn't worse.
If you want shallow DoF, you can get plenty of m43 and APSC (16/1.4, 56/1.2, 90/2) lenses for shallow DoF. If you want razor thin DoF - nose sharp, eyes blurred - you need <=1.4 35mm glass.
If you want full body portrait with blurred near background you need medium format lenses (or far away background).
If I build a lens that will cover a hypothetical 16MP sensor with good quality over the whole sensor, it will also cover a hypothetical 16MP sensor of half the dimensions. However the smaller sensor demands a higher optical resolution (line pairs / mm) than does the larger to resolve those 16MP with the same clarity, and so the smaller sensor will deliver lower effective output resolution (again, in terms of resolvable line pairs) than will the larger sensor given the same glass.
And if I'm searching for shallow depth of field, again the larger sensor has inherent advantages. Physics isn't your friend once you start trying to build arbitrarily fast small sensor lenses to replicate what's easy with a larger sensor lens.
I'd be delighted if these concerns weren't true; my m43 camera is much lighter to cart around than my FX one :) And yes, we can now get DR and noise performance from a smaller chip that we used to not be able to with a larger chip - but there are definite advantages still to the larger chip that won't go away.
Faster lenses help up to a point but since f stops of under 1 aren't really a thing, you're not going to replicate a large sensor with a fast lense with a smaller sensor.
Higher Resolution, yes if you need 50mp because 24mp is not enough to print 3m x 2m.
There's other quality issues in an image though, edge definition and depth of field for example. All things being equal a larger sensor with equivalent glass will always provide better edge definition, and having both 35mm and m43 chip bodies I would say the difference is noticeable. And for depth of field it depends what you want. I can isolate a subject much better with a large chip camera, but that's no use for a macro image where the small chip camera is better.