The truth is that modern systems are becoming increasingly complex. The computer is now similar to that game "Jenga" where you have all of these pieces relying on many of the others. Pull out the wrong piece and you have an error, pull out a correct/necessary piece and you still may produce an error. The more complex the system the more time you are likely to spend thinking of ways to make your code more robust, and hopefully more secure as well. Speed would be nice, but I think speed takes a back seat a lot these days when you hear in the news that "XYZ" company was hacked into and 6 million customer's credit card numbers were stolen.

Your clients may not want to hear that their program needs to be secure, robust, etc.. But you could tell them that their car does not need seatbelts and airbags nor their house need locks and doors... because who wants to hear all that?

If you are over-thinking you are going about things the right way, except that you need to pick a strategy that seems "concrete" and just go with it.