Maybe if you include every application ever written, including every variation of "hello world", but if you are claiming that most serious production quality software could be written by a CS student who is simultaneously working on other classes, I'm gonna have to disagree with you.
There are plenty of open source compilers that I can copy and paste whatever I need to. I don't get why you think this would have any level of difficulty?
Of course I couldn't make a brand new compiler that was better than what's out there...
Just like a game engine, I could clone one of the thousands of engines out there pretty easily - making something better or novel would be difficult. Just making a bare bones clone of what already exists by referencing documentation and pre-existing code is relatively easy now.
Yeah, when I made a mediocre 3d game engine 20 years ago, it was brain breaking difficult work. I can make one infinitely better in a micro fraction of the time now because most of the hard stuff is done and can just be looked up now.
Do you not agree?
Sure. You can clone gcc and build it. You can close a game engine and use it.
That depends on how you count. By number of programs that may well be right, but that's not what matters in terms of impact on the industry, as software value roughly corresponds to the number of people working on a particular piece of software (or lines of code, if you wish). By number of people/LOC most software is not in the "simpler than a C compiler" category.