Xplat FWs are just technical debt to prove a concept. Once you find critical mass the first order of business should be converting to native so you can remove that entire layer of additional complexity. Similar to paying down student debt to minimize how much interest you wind up paying on them after getting a good job.
IMO this should be the natural order if you size use it at all, not the emergency case.
There are different ways to think about complexity. In terms of the code that's being executed, certainly using a cross-platform framework is likely to result in more complex code as the final output. However, for apps that do not need to use a lot of native features, cross-platform frameworks can significantly reduce the amount of code that needs to be written.
It also means that the entire mobile team can become experts in one framework rather than needing iOS and Android folks. That said, it's certainly still helpful to have deep platform knowledge to debug/optimize in certain situations. But I think the point where using a cross-platform framework stops making sense is going to be very different for different applications.
IMO this should be the natural order if you size use it at all, not the emergency case.