That isn't really true, software projects fails all the time even when everyone knows what to build. A recent well known example is Cyberpunk 2077, its engine c

That isn't really true, software projects fails all the time even when everyone knows what to build. A recent well known example is Cyberpunk 2077, its engine couldn't handle anything less than the latest hardware causing tons of bugs. If you know what to build and that thing is something trivial that many has already built before, then sure it isn't hard. But any time you try to push and deliver software doing things that other companies doesn't it will be hard. If your business suite covers more cases than all other business suites then that is impressive and hard, etc.