The thing you forget is that every new player is pretty much shit at the game, so it doesen't really matter if you can't combo properly as ryze (tbh the combo isn't even that hard, just slam your face on the keyboard and you'll do decent). As for the build path, it doesent take a genious to look up a build guide for ryze, and see that you go tear into rod into frozen heart.
And as for Sona going OOM for newer players, what champion doesent? Mana management is a thing new players rarely know, so you can easily go oom on every champion, unless you build stuff like chalice.