Why would an orbit decay without something to slow the spacecraft down like an atmosphere? The problem is that any object we launch from earth has a lot of orbital velocity, which makes it almost impossible to hit the sun directly, you would have to use a lot of complex gravity assists from the inner planets to take away enough momentum. Using gravity assists to accelerate outwards is much easier
That’s what the premise of this post was. It’s a common saying to “shoot something into the sun”, which sounds easy at first but is actually quite hard to do. That’s the joke