Native Android and iOS development is sort of in the trajectory of where Windows or Mac desktop app development had gone a decade back.
While Adobe still will need to make desktop apps, no new startups are launching as a desktop app (Electron even if they do)

The management perspective of "less developers, both platforms" is a bigger pull than anything else to go for Flutter or React Native.
The relatively easier migration path for React web devs to come and lend a hand to mobile app dev is a big factor too.

Older apps that are on native platforms for 8-10 years, (most really big apps, with 100M+ users are all either fully native or significantly native). They will most likely remain so. No need to rewrite, plus they might be using native level APIs, and performance is important.

Early stage startups, unless having native Android/iOS developer in founding team, will hardly ever start off with a native app anymore.
Unless in a few niches like
- camera app
- video streaming (with lots of custom codec, DRM)

It also means the general quality of app experience (the median UX if you so say) is coming down a bit.
My experience especially in SF was that many new apps, made in RN, worked abysmally bad at some places, especially on Android.