They do need more variety.
It's exciting watching different tactics and strategies play out. It's exciting watching the top players adapt their games to different courts.
Serve and volley tennis was great to watch, as is baseline tennis.
It's also great when an underdog plays the tournament of their lives and makes it to a grand slam final.
None of these are happening anymore. Don't get me wrong the Novak/Fed final was awesome to watch, but there have been many tournament finals in recent memory that have been monotonous. The same patterns over and over and over again.