I am not parent commenter, but your comment really struct the chord here. I failed to convince 2 people (my mgr and team-lead) for our relatively-green-field project 2 years ago to use Kotlin... Thing is - same people killed an idea to use Lombok as well. So it is an uphill crawl no matter how "big" is the change - it is how comfortable people are with what you are proposing, and where they (and you) are in a command (aka responsibility-and-headache-if-something-new-goes-wrong) chain.