Yes, this is actually quite common. What I've seen happen, twice personally, is a large company asking teams of developers to work on a codebase they can't real

Yes, this is actually quite common. What I've seen happen, twice personally, is a large company asking teams of developers to work on a codebase they can't really understand, and have no chance ever to, because the code has basically got to the point of no return, in terms of messiness. What happens next IME is that progress mostly stops, and the company loses market share rapidly.