I’ve used one at a previous company, and while it gave us structure, it also created a false sense of progress. We’d hit “Level 3” and then people stopped pushing for improvements, almost like we’d arrived.
What worked better was when we switched to using maturity indicators as a conversation starter, not a report card.
We started running internal reliability reviews where we graded ourselves honestly, but the emphasis was always on “what’s next?” rather than “are we there yet?”