If you are already in a reactive framework, why would you change to virtual threads? Those frameworks pool threads and have their own event loop so I would say they are not suitable for virtual thread migration.
Yes, if you're happy with the reactive frameworks there's no reason to migrate.
Most people, however, would love to remove their complexities from their code bases. Virtual Threads are much, much easier to program with. There's downsides, like not being able to easily limit concurrency, having to implement your own timeout mechanisms etc. but that will probably be provided by a common lib sooner or later which hopefully provides identical features to reactive frameworks, while being much, much simpler.
I've not looked too deeply. We use the eventloop model, and we're guaranteed that data is only mutated by a single unit of work at a time which means you don't need to use any concurrent data types, volatile etc. This is great for micro performance.
Does the same apply to virtual threads?
Edit: I think I answered my own question. Java virtual threads have the same memory model as regular java threads so yes, I need to use the same semantics. That rules replacing the eventloop model for us.