Biab certainly does make it easier but good midi's can be very useful. There's some floating around that are top notch pro quality like the ones posted by Doug Mckenzie in Australia. Check him out, just Google his name. He has his own website and he's on Youtube with good Biab video tutorials. He's a master level jazz pianist and has tons of great Biab and midi files.
You can usually tell if the midi is a good one even of some of the instruments/channels/CC volume etc are off. That makes them worth the time to rework. I usually look for pro quality rhythm/percussion tracks and equally pro level live solo's. A good midi solo is worth it's weight in gold as a learning tool because you can see the notes playing on the keyboard display and in the notation and it doesn't matter what instrument the solo is. You can pretty much adapt any solo to another instrument. Since it's midi you can use Real Band and put a killer rhythm track from a midi into a Biab arrangement with some editing and come up with some really good stuff. I've mixed a midi drum track with precise drum fills with a Real Drum percussion track and made it sound like Pancho Sanchez.

Bob

Biab/RB latest build, Win 11 Pro, Ryzen 5 5600 G, 512 Gig SSD, 16 Gigs Ram, Steinberg UR22 MkII, Roland Sonic Cell, Kurzweil PC3, Hammond SK1, Korg PA3XPro, Garritan JABB, Hypercanvas, Sampletank 3, more.