"Show me a player with a great first serve, and I will show you a great player! Show me a player with a great second serve, and ill show you a champion!" or so the saying goes( the exact quote is eluding my memory). We have a tendency to get smitten by the huge first serve of the likes of Nick Kyrgios that lead to massive number of aces or free points. The art of winning your second serve points seems to be highly underappreciated. Here is a deep dive into the mastery of winning points on your second serve by the "father" of tennis statistics Craig O'Shannessy: https://www.braingametennis.com/the-art-of-winning-2nd-serve-points/
Enjoy!