You can tell a lot of the sounds were generated through an arpeggiator module but they still have to be programmed in the correct root/key and depending on the song's root chord, you can create some interesting incidental harmonies based on your choices. While it's partially automatic, it's not completely so. Part of being an observant music listener is picking out those interesting harmonies that are created incidentally from other fundamental music structures. So yes, those melodies are there, but it's up to YOU to try to and hear them. If everything was spoon-fed and obvious, everything would sound like Blink 182. A good song in any genre, IMO, is one you can listen to over and over and appreciate differently each time.
Classical Music Theory has laid a foundation that existed for nearly 500 years so in the sense you are talking about, most music isn't "good songwriting" in that it utilizes this foundation. Jazz is the first truly antithetical music (in the Western World) to take Classical Theory and completely ignore every rule it ever made. Working within a framework of theory doesn't make music necessarily bad; but it will almost certainly be so if the listener doesn't step back and just hear the song as a whole.