The problem isn’t that shoryukens are easy to perform, the problem is that a shoryuken occurs when performing another move. For example some characters cannot walk forward and throw a fireball (which is a huge issue imo), unless they pause awkwardly at some point during the execution of the move.
You’ll see people say to start the fireball from down back, you’ll see others say to continue the arc to up forward - those might appear to be a solution due to the slight delay they add, however when done quickly enough they still end up in a shoryuken.
Lots of times I wished that there was a “neutral” button that when pressed would clear the entire back-buffer of commands whatsoever. So then you can walk forward and throw an hadouken without having to pause, something like release forward then immediately press neutral, then QCF press Punch.
Contrary to popular belief, moving the stick/pad into the neutral position does not clear the previous directional inputs.
The inability to walk forward and immediately throw an hadouken isn’t only limited to SF4, this issue is in previous SF games as well though not as noticeable or problematic, as SF4 is more lenient with input timing.