Hmmmmm........I agree. But we are keen photographers with an eye to getting the maximally pliable image. Most clients do not care about the technicalities and it comes down to 'do I like the image'. We get carried away with gear and technicalities to an extent that passes the client by.
I presume your argument here is that the Olympus MFT system has better dedicated lenses than an APS-c system ? From my experience in comparing these the larger sensor of the APS-c still wins hands down when it comes to large output. Also I've found that these small, high density sensors still require a good steady tripod to optimise their output.Quite a few professionals will disagree. E-M1 mkii with 7-14 f2.8 versus a 5D4 with 16-35 f2.8. Or even EOS-R with 16-35 f4. Then add a couple more lenses (such as a 60mm macro and wide primes and even a standard zoom) plus the filters and spare batteries and other paraphernalia then lug it all for 6hours cross-country.
I agree that it seems other mirrorless marques are narrowing the gap but the gap is there - and when it narrows more I suspect that those shifting to MFT may switch back and get the best of both worlds but we aren't there quite yet.
Perhaps you can point me towards some of these professional landscape photographers who are using MFT and I'll be able to get a better understanding.