If I was a pro would I use only a Kiev? NO! If I was a pro would I only have one Hasselblad? NO. Have I ever had a difficulty with a Kiev? NO. There are lots of working kiev cameras out there. Unfortunately the folks who own these cameras do not write about their good cameras. You hear about the complaints and failed cameras and bitter owners.
As for other brands being more reliable, maybe, maybe not. No they are not as cheap yet. It is still cheaper to buy a bag full of P6 or B mount lenses when others own 1 or two from their brand. The glass for a Mamiya (very old Mamiya) is still more expensive than russian glass. People say it is better but I bet you could not pick out like images made with my gear and mamiya gear.