I don't think this game needs to strive for complete reality, I think it's more fun this way. Especially since if you disable the possibility of a dropshot return, it will be far too easy for serve-and-volleyers to hold serve. I personally use the dropshot return, since it's pretty much the only chance to break, and I've had a lot of fun points because the point could go on a bit longer, rather than just a serve and volley put away. If the dropshot return gets disabled, then the effectiveness of serve-and-volley should be lowered, for balance.
This game is already very realistic in many ways, but I wouldn't mind if complete reality was the goal, but then a lot of the games dynamincs would need to be changed, and I think it would be very hard to make a game that is totally realistic and yet has good playability and fun factor.
But in general, things don't need to be changed just because someone can't handle something, it takes some practice.
I have many suggestions, like putting more emphasis on different styles, power hitter, volleyer, grinder, varied, etc. but they really would need to be equally effective styles, so that a player could choose what he/she finds most fun to play without having to worry about it being inferior to others.
But this was another story.
The point was, return dropshot can't be disabled, since it's an essential part of a returners tactic against serve-and-volleyers, alongside with lobs and sometimes some suprisingly accurate regular return shots that the server can't reach.