For racing Enduro I’d say you need some good DH skills and a good capacity for short sprints.
A road bike won’t help you for that first one but a road bike can be great for the latter.
I’d be forgetting about doing anything long distance and flat on your road bike and just stick to something with some descent incline or working on short busts of maximum effort.
I’d disagree with that. My (very limited – just two in fact) enduro experience has been that you’re pedalling for 2-3hrs with a few short breaks in between short bursts of high energy.
So yes for interval training for the downhill bits, but don’t neglect the distance rides for stamina training for the ride back up!
OP – exactly what riding are you doing right now – duration, distance, road types, any training routines or just riding? This will help give you specific pointers