I switched from my Nikon D90 to a Sony A6000 mirrorless and loves the more compact size and weight. Also way better autofocus.

Had a bit of money come in recently and also bought a A7III with 55mm 1.8 Zeiss and Sony 28mm 2.0.

Absolutely loving it but its definitely the first time my kit is way better than my skills, im nowhere near pushing its capabilities.

I also have a Sony, they are very decent cameras and work well, the problem is availability of lenses. Seems Sony don't give the independent lens manufacturers access and that means non-Sony can be more miss than hit.

I'm still a little confused over the "smaller camera" aspect of mirrorless systems...as inevitably you still end up putting a massive lens on the front of it anyway?

That depends, there are huge lenses available, and yes, putting one of those on would be a bit pointless. I still have my old massive 150 to 500mm zoom somewhere but can no longer carry the thing. Then I still have my 1.2KW hammer drill... The Sony 70-200mm is actually fairly compact. putting on a 30 or 60mm and it is fairly small. Getting rid of the mirror and prisms certainly reduces weight a good bit and increases reliability. For normal use by the average person in the street I would still suggest a mobile phone.

Then I had issues getting new lenses from other companies that both fit the Sony and work perfectly. Even supposedly 'compatible' lenses have had issues. I got sick of that and went for the cheapest Canon, a 100D, which works perfectly with all my Canon fit lenses. Never looked back. Although I'm now thinking of getting an upgrade.

Ive upgraded to the A7iii now and absolutely love it, but its not much smaller anymore, feels a lot like my D90 but way better tech.

I havent found lenses to be lacking, I have the Tameron 28-75 2.5, Sony 55mm 1.8 and Samyang 24 2.8. All of which I absolutely love and none which are particularly large.

Sony has brought out the a7s III. Any of you keen on this one? Lots of youtuber's and camera folk seem to be loving it.

A7sIII seems to be aimed at film making. Being twice the price and having lower megapixels I dont have a lot of incentive to switch. Still super happy with the A7iii.

Id love to see the new menu system and improved Eye-AF features come to the A7iii in an update though.

On devices like Cameras and tv's between different models they should be more universal with the OS and easier to update with more updates. BUT in this area manufactures from even just 1 year old tv's the OS seems so different you get different types and version of updates where some simply do not make sense.
I hope so because looking at reviews I know what you mean, but if they don't it's silly they don't.