I'm sure it is possible to have an artistic layer of software management that reduce everything to "write me a function that passes this test", which you could outsource to wherever. But having reduced all of the code to that level you have done all of the hard work in writing it anyway, haven't you? By involving the all of the junior devs in that reduction process, you are also teaching them how to do it, so they can be he next 'architect'.
An interesting and sort of related aside: I do some work with a company that makes old fashioned 'Enterprise software'. Their process seems to be that the back end dev gods write functionality that is convenient for the database, and then the front end people make that accessible to humans in the most convenient way for them. So instead of working the way humans do, the humans have to work the way the database does! When you talk to their back end devs, they talk down to you like you are an idiot for not following the way they work! Their db implementation is actually pretty good, the application is only really usable to people that can write SQL, however! If their API didn't also suck it would be tempting to re-skin the whole app.
