M43 has two limitations because of its small physical size, namely, low resolution and weak low-light performance.
Whether these are problems, it really depends on use and needs.
Both true, but neither a problem for me.
The resolution is plenty, IME.
I completely disagree about the potential about lenses and sensor resolution. Optics are NOT only about sharpness since IME (58 years now since my first camera) flare resistance and boke are at least as important and these are not always good on sharp lenses, so obsession with sharpness isn't necesarily going to get good photographs. In addition, whilst anti shake provision in cameras/lenses has been the biggest gain in photography in the digital age IMO if you want to achieve the
full potential of high resolution lenses and sensors a heavy solid tripod is necessary and few people in the phone camera age even have one never mind use it and are wasting the potential of their camera a lot (all?) of the time.
When I first took up digital photography I did a lot of comparisons between prints I made in the darkroom and digital files on a printer at various resolutions. For prints at A4 (near to the 10"x8" old standard) I found more than 3.5 megapixels to be unnecessary at a normal viewing distances and above 6 megapixels there was no visible increase in detail under a loupe.
Of course if you only look at pictures on your computer screen or email them the requirements are quite different, and opposites!
One of my favourite little photographic excercises is taking a panorama from the beach near my daughter's house on Anglesey over the Menai Strait from the Great Orme to Bangor. I have done it since she moved there years ago and have panoramas with many weather conditions. I have tried several techniques and camera/lens combinations. The best success has been with Leica 50 and 90 mm lenses. The 4/3 lenses use computer correction of distortion, which is fine for single shots but doesn't work well with stitched shots in Photoshop, though I only tried it once and maybe one of the other lenses I have needs less correction. I have also tried Canon and Nikon for this shot but their lenses are markedly inferior to the Leica ones when super resolution is the goal. The files, blended and trimmed tend to be around 90 megapixels and look great on a high resolution screen, but even then the atmospheric conditions, humidity in particular, have a considerable influence on the actual resolution in the picture of the more distant elements on the Snowdonia hills.
As you write, the "weak" low light performance is a matter of use. As an old bloke who used 64asa Kodachrome for decades even the base ISO of 200 is "fast" for me. I have certainly had some picture from 4/3 where the noise is disappointing but for most of the things I do it is a non-issue, and to some extent the poorer low light performance is offset by the 4/3 lenses usually being faster.
Overall I am thrilled with my 4/3 camera's utility and the combination of size, weight and some superb lenses, some of them not expensive at all, make it one of the most useful cameras I have ever owned (and I have owned lots as an ex-collector of old ones).
Yes, overall the Leica M10 is better but I have sold the long heavy Leica lenses I used with an adaptor since I never used them - it is still the best for normal photography but the 4/3, admittedly mine is an Olympus OM-D E1 mk2 which is hardly cheap, has superb lenses and more or less instant autofocus and is perfect for family snaps plus wildlife pictures.