being successful in a legacy codebase is a lot like having the right attitude to have fun a the Renaissance faire. it's a delicate balance of modern sophistication and ye olde whimsy.
You can take part in the festivities like watching a blacksmith make what you hope isn't a cast iron chastity belt but don't take a shit in the middle of the street. Much like you can spin up a .net 3.5 app pool but don't use Microsoft's Enterprise Library for .net 2.0