According to the TNG science advisers, 24th century ships were faster than their 23rd century counterparts and how warp factors were calculated changed.
So if "transwarp drive" was merely the name of next gen warp drive, it may have been completely successful.
That's true. And it's never really explained what Excelsior's
engine was supposed to do. Could it create conduits to travel through space like the Borg did? Did Starfleet even conceive such an idea during the twenty third century? Thinking about continuity, it's likely someone would have referenced the idea when talking about the Borg, and an explanation of why the Federation did or didn't have transwarp drive would have been given.