They simplify it by saying "he" never finished his films.

Not only is it an extremely complex and perilous process with endless ways to fail or succeed - but it's a team effort, including the investors and their nebulous agendas.

More or less what he said, the more experience you get the less spontaneous your efforts are because you already know how much work is involved in pulling it off. This is why I haven't animated seriously for years - it needs to be worth it.