Speaking of Ryu, his options against shield have to be either shield break from collar breaker or grab, which he can't get much out of.
His approach with that spinning kick is not safe if we can shield it in time. While it can plow through projectiles, then we must understand the range at which we can fire missiles safely. Just like against fox, whom missiles aren't safe against if he is half a stage, ryu has a distance larger than we expect where missiles are punishable. If we get punished for firing a missile, then we need only change ourselves. Eventually, they will never have that opening and so approach with hurricane kick will be punished.
Canceling focus in the air can be punishable. Punishing it really depends of where we are relative to ryu, and how close he is to the ground. If he jumps in the air, he will eventually have to land, and if he spams focus to land, then we can predict it and find a countermeasure. For example, air dodge spammers will get destroyed by cross-up pivot grabs on their landing. They expect an aerial and air dodge, but we bait it out and get that grab. With ryu, he gets a slight mix up tho, with forward-dash-cancel-focus (FDCF) and backwards-dash-cancel-focus (BDCF). The mix up isnt even that great. I have found myself dash attack punishing that plenty of times, but that depends on what we read and if we opt for an early dash attack, or late dash attack. Considering a late dash attack, which I prefer, when they FDCF, if we run up and dash attack, they will either be too close and we cross-up, but we can't be punished since we are too far behind, and we are in a close-quarters neutral situation. If they BDCF, they get hit by that dash attack. If they hold through focus without canceling, we still cross-up and may be too far for b-reverse focus to hit, or we shield it in time, and if they don't reverse the focus, we get an easy punish.
A focus approach is punishable just like any other movement option.
Zair is super good against his recovery. We can also break his fireball with our zair, but if we get too close, the fireball will go under, and we will get hit. So, yes, as
Xygonn
stated earlier, we get punished if we are impatient. Patience and zair can keep ryu out.
His aerials and combo game on samus is still strong, but it's not like we don't have good follow-ups for our moves as well. We definitely can't be unsafe on shield against ryu, but that goes the same for the rest of the cast. He just has a stronger punish. We really can't just throw out grab in this matchup tho, which sucks. If we miss a grab, we get that uppercut to the chin, and possibly lose a stock due to a whiffed grab. Overall, this matchup is just one where we make the ryu approach unsafely and punish. If we go too hard on the offensive, we'll get beat out playing ryu's game plan.