I really don't know what you mean by a stepped approach, but it could be part of the problem. Law 13 says "an opponent who deliberately prevents a free kick being taken quickly must be cautioned for delaying the restart of play.,"
The referee has no choice in this, he should book every time.
No game is referred with an absolutionist view of the laws. In fact, refs are encourage to consider the spirit of the game, and to create a fair flowing game. That's why every( strict foul) for a minor tap doesn't result in a free kick; refs set a threshold and the good ones apply it consistently.
Likewise a letter of the law approach to yellows for offences like delaying the restart in play doesn't work either. A stepped approach is about managing the heat in a game. (Yellows don't defuse situations, but can inflame). This refs are coached to follow a stepped approach where appropriate; ask, tell, enforce.
(Remember that if we card a player, we are also preventing the quick free kick, which punishes the fouled team)
It's a shame that there isn't more education for the spectating public around those concepts. Ifab explain it lightly here: