If you have been hired by a professional corporation and you are getting paid to write the code (I presume I am talking to a basement dweller by your ignorance) then YOU ARE NOT TOO STUPID.
You have CLEARLY never actually put your fingers into someone else's complex code. Man I gotta say I would give you a good swift kick in the nads if we were speaking in person because you are just SO STUPID.
You are just UNAWARE of the software authoring process. Developers on projects come and go. Some of them leave good maintainable code behind. Some leave undocumented messes. But if you are on the team and you have resources of other developers at your disposal, you work with them to understand the odd code. And THEN after you have looked at the code and your comrades have looked at the code and you ALL throw up your hands in despair, then it is THE CODE that is the problem, not the developer.
Hey YOU can pretend that developers work in a vacuum. You can pretend that they don't work together. You can pretend that professionally hired and paid developers are "stupid". And you can GO TO HELL for your arrogant stupidity.