Large corporations with a captive market inevitably reach the digital bureaucracy stage, where the exaggerated mass of their workforce breaks under its own weight, and they become inept at doing basic things. This is a great thing for small startups, else we would only have a single huge corporate conglomerate doing everything with cutthroat efficiency.
Add to that various attempts at fixing problems, adding features, partially removing unsuccessful features, supporting old systems, framework/library migrations in various states of completeness, different developer's ideas of how to do things, and that rockstar developer who wrote really obscure code and then left to grow pomelos, and you have an incredible mess without even having to bring in company bureaucracy.