This is feedback specifically for groundstrokes, though obviously other things need adjusting as well.
-Topspin Shot-
Too much pace and too little risk. A normal (no LT/RT) topspin shot should mostly land within ~5 feet of the center line. This is the “rally” shot. Right now they land closer to the sidelines than they do the center line, but this is not how rallies happen in tennis. A good chunk of normal topspin rallies land near the center line, and only when an opening appears will a player go for the sidelines.
And that’s where the LT/RT comes in. LT/RT should push the landing area to the sidelines with SOME of the landing area being outside the side lines. That better your groundstroke stat, the less landing area will exist outside the sidelines.
In short, most safe topspin shots should land near the center line. Most risky topspin shots should land near the sidelines with some landing out. Using a LT/RT topspin show whole standing still would carry little risk of going out, but doing one whole running or reaching would give a bigger landing area would lead to more outs.
-Flat Shots-
These are the straight winners. Topspin shots can be winners, but flat shots should be the “go all in” winners. The current pace of the topspin shot should be given to the flat shot. Flat shots should be landing out a lot, but not when the incoming ball is lofty and/or slow. Using a flat shot during a normal rally should be incredibly risky but if the opponent hits a slow shot back, a flat shot should be much safer than it is now in the current game.
-Slice Shots-
Just needs a big rework. First, the animations are pretty bad, but beyond that the ball physics are way off as well. Slices should be sharp and flat. Current slices in the game act like a feed when starting a practice rally. They need to be sharp with more pace and bounce much deeper into the back court.
Now, defensive slices should exist. And those should perform similar to how the current slices do. But a normal offensive slice just doesn’t exist in the game.
-Conclusion-
Topspin shots need to be slower and may riskier when using LT/RT. Flat shots should clear the net and have the oace that current topspin shots do. Slices need batter animations and should have more pace and depth.