React Native is terrible for maintenance because old libraries rot in extraordinarily troublesome ways; typically the choice of libraries is between obviously already dead but it might still work today, amateur efforts with no real support, currently popular but who knows what will happen in two years, and do-it-yourself.

Specific React Native circumstances and design choices, like the coexistence of alternative Javascript interpreters (e.g. JSC and Hermes), different tools for the same purpose (e.g. npm and yarn), separate organizations (e.g. React vs. React Native vs. the "standard library" vs. certain tools) and radically different code styles (e.g. old class components and new function components that are nicer but without feature parity) add risk and pointless maintenance.