You are wrong to label someone who hits mostly slice as a pusher. One of the most aggressive players I know hits mostly slice forehands (pretty flat with an element of slice). He times it to perfection, just clearing the net and with great placement and hits more clean winners with it than most do with topspin forehands.
Steffi Graf only hit slice backhands and won the most singles Grand Slams by some distance.
I hit topspin from the baseline but have never been great as short ball putaways with topspin. I have developed a sliced forehand putaway instead which is very reliable. I saw Federer using exactly the same shot a few times at Wimbledon this year and he ain't no pusher !
Also don't kid yourself by labelling players who use long rallies to tire you out as pushers. I can play various styles to suit the situation. If I am playing someone which good groundstrokes but iffy fitness compared to me my goal in the first set is to make every rally as long as I can - even if that means prolonging points I could finish. If I can wind them in the first set then the next sets are a cakewalk. Ferrer and Nadal do the pro equivalent regularly enough.