I switched from a heavy hybrid to a road bike and can empathise.
Road bikes are responsive and light and great fun but they take a wee bit of getting used to. Persevere and ride in the hoods for a while.
My hybrid feels like a tractor now - in fact I'm planning on getting an orange light for the back.
I don't much like the idea of doing the commute on the MTB again. I couldn't believe how little effort it took to get the bike moving, and the hill about 5 mins from my house which usually leaves me out of breath and very hot was a doddle. It was a fun ride though, except for avoiding the awful road surfaces I'm used to just trundling over.