I'm thinking more like programmers working at the IRS or SSI or something like that, where you have million line long decades old codebases. Not anything that Google or Amazon would write. Applying a DI framework right from the start may actually be a best practice--that allows the codebase to evolve under the next 10 years of contract programmers--instead of just being the YAGNI that it would to anyone in the tech sector.

Although you might say that microservices are like a distributed DI framework that would let you rewrite or mock components provided that the rewrite/mock adheres to the API framework (curiously, I've actually seen that used in tests with a quick and dirty in-memory sequential unauthenticated server used for testing clients where the server passed the same API test suite as the real server).