I got the opposite kind of lens, one at the upper end of what you can wrangle in your hands. If your lens is big you have a heavy pack, look like a dork, can't hold it steady, all that. There is a lot to say for a camera that is easy to handle.
To take your SEL35F18F as an example, the lens weighs 280g. The Nikon DSLR equivalent, "AF-S NIKKOR 35mm f/1.8G ED", weighs 300g.
To go to extremes, Sony's SEL600F40GM weighs 3kg and so does Canon's "EF 600mm f/4L IS III USM" (admittedly, Nikon's equivalent weighs 4kg).
I'm not saying this to prove you "wrong" or anything, a Sony A7RIV weighs 665g to a Nikon D850's 1kg or a Canon 1DX Mk3's 1.4kg but switching to Sony might just be the difference between a 5kg kit and a 4.7kg kit: it's still pretty heavy.
I'm just pointing this out because when I was starting out I heard a lot of people talking about how small and light mirrorless cameras were. I think at the time this idea was focused more on cameras like the Olympus OM-D series. Amateurs/enthusiasts (including myself, who owned an OM-D) often didn't realise that one of the major reasons an OM-D kit was much lighter than a DSLR kit was that it was optically less capable due to the differences in sensor size. A big part of the reason an 17mm f1.8 MFT lens is so small is that it isn't equivalent to a full-frame 35mm f1.8 the way many people thought it was. It's more accurately equivalent to a 35mm f3.5 which could be made similarly light for the larger sensor, if anybody wanted that (but few people want that).
What they didn't point out is that those bigger heavier lenses are bigger and heavier because they are more recent, and the camera sensors are so detailed that the cameras need fantastically sharp lenses, which means that they are bigger. Also, people's expectations of the quality of lenses has increased. So, they could make some small light lenses, but then someone would pixel peep and complain about how blurry they are, when in actual fact they would be just as sharp as the old DSLR lenses, but the cameras are more able to reveal their shortcomings.
The accurate autofocus is nice but I would rather have an older flagship DSLR than any modern mirrorless camera. The only exception I might make is for a more recent Leica M camera, but that's only because I've sold one and would like to use those nice tiny little lenses again.
But are these lenses and bodies actually designed that way, or do they keep the old dimensions because of backward compatibility?
Mirrorless has several advantages: no more mismatch between the focus sensor and the CMOS sensor, no more mirror lag, viewable area matches CMOS sensor area perfectly, electronic viewfinder can show the image as it would be after exposure (making over/underexposed areas easy to spot while composing the shot), and most importantly it allows for much more compact lens designs because the last optical element can be much closer to the sensor since there is no mirror in the way.
Viewfinder lag has not been an issue anymore since 10 years ago. And with recent CMOS sensors having phase-diversity elements, autofocus can be as fast as with DLSRs.