Ryze is your OG battle mage, which means you have to treat him like a fighter. But instead of wanting to get right up to the enemy, you want to get right in the middle of your max range, and theirs. Because unlike a fighter, you aren't too tanky. The most common Ryze build is
with some defense from
or
. Besides some minor defensive stats, you are building damage items with strong passives/actives that can be defensive. But when fighting someone like Olaf or Darius, you need to dodge their abilities, while also pelting them with yours. Because the moment they get you into their damage zone, you are gonna die.
To answer your question, I would say that Ryze is a hard champion. There is a specific reason why Ryze has such a low win rate across most levels of play except high ranked. His damage, while high, only shines during extended fights, which don't happen if he gets caught out or focused hard. Early game you don't do much, you can get some good damage off, but most of the time unless you capitalize on it well you will run out of mana before you can kill someone. But once you start stacking mana on mana, you start doing a lot of damage. Orb walk around your enemies, keeping melee champs off of you with E --> W --> Q for a better snare and movement speed. I find Stormraiders surge to be quite good on Ryze because you always want to be moving quickly, and thunderlords doesn't do much for you due to the fact that you don't really burst, you whittle opponents down. Ryze is also fairly good at 1v1ing, but only if he can keep opponents in his ring of damage, and out of theirs. Most adcs will just out damage you late game, so you need to rely on your team to handle them. Ryze is just a different champ then what he used to be, and he isn't a face roll as he used to be.
I have to disagree with your comment on his ult being useless in solo q. I have done plenty of good ults where the only indication I gave my team was a lot of "coming" and "help" pings. Even won the game off of a few. It, like any utility ult, requires your team to know how to capitalize off of it well. So yes, there will be duds, but the pros outways the cons.