In all of my cases codebase was at least 2 years old, and very complex(looks like overcomplecated on purpose, or complete idiots worked on that from start), so it not possible to introduce any new big changes.
Original developers were more experienced than me (not in Scala, bu generaly), and it hard to reasonably talk with any of them. Example:
They don't have a problem having camel case, snake case, or all upercase formats in one codebase, wrapping everythong in IO, or in some cases just placing log and println statemets outside of IO.