Hmm, not sure I buy this, sure it's not as fast as going native on every platform. But let's be honest the alternative isn't 3-4 native applications built with care for each special little subgroup. It's a MacOS only app in the US market or a Windows only app everywhere else.
Businesses don't have an unlimited amount of money to spend addressing every tiny market so I'd say the complainer's focus should be on building a better X-plat story if they really care rather than whinging that some application isn't built to make the most of the 0.1% of the addressable market they find themselves in.