The "get it back" strategy starts to become ineffective at strong 4.0 level. At that level, you're required to go on offense and make plays especially on your serve. At 3.5 and low 4.0 you can just play defense and wait till someone makes a mistake or feeds a ball.
Rally speeds also play a big factor to level as you can beat a 3.0 with high pace and poor placement whereas a 4.0 would need decent pace to beat an easy poach as well as good accuracy.
Also, pointless errors regardless of level is never a winning strategy.
I define a pointless error as an error on a "rally" ball or an error on trying to hit a winner that didnt have a realistic possibility of going in. An error on a realistic chance of a hitting a winner is a good error.
What you say about the serves are true too. While most scrubs build their ridiculous first serve first (and then tap it over on thier second; common in 3.0 and even some 3.5), any decent player will build a strong second serve and use it twice.