IMO, React's popularity has little to do with productivity in the context of what other tools are available (many of which we never even heard about). It's mostly about network effects. Popularity is the primary reason why companies use React as it suppresses developer salaries by making devs more interchangeable. It creates liquidity in the market for dev talent due to shared familiarity. Had the similar kinds of network effects existed around a different, better framework, all companies would be much more productive. And even then, I would say the benefits of network effects are greatly exaggerated.
Also, it's important to note that many developers who are good at putting together functionality in React quickly aren't necessarily good developers in the more general sense (in the long run). This can cause problems later in terms of security, maintainability, performance, hiring (due to complexity of the software itself scaring off prospective hires; familiarity with the stack isn't everything) also there are concerns about operating costs, vendor lock-in and scalability.
Also, it's important to note that many developers who are good at putting together functionality in React quickly aren't necessarily good developers in the more general sense (in the long run). This can cause problems later in terms of security, maintainability, performance, hiring (due to complexity of the software itself scaring off prospective hires; familiarity with the stack isn't everything) also there are concerns about operating costs, vendor lock-in and scalability.