For many syscalls, the primary overhead is the transition itself, not the work the kernel does. So doing 50 operations one by one may take, say, 10x as much time as a single call to io_uring_enter for the same work. It really shouldn't be just moving latency around unless you are doing very large data copies (or similar) out of the kernel such that syscall overhead becomes mostly irrelevant. If syscall overhead is irrelevant in your app and you aren't doing an actual asynchronous kernel operation, then you may as well use the regular syscall interface.

There are certainly applications that don't benefit from io_uring, but I suspect these are not the norm.