They had a rescue vehicle on standby. And by 1973, Apollo wasn't really "new hardware".
AFAIK, they lost 2 out of 3 aft-facing thrusters on 1 of the 4 pods so, if the math doesn't fail me, that would be 2 out of 12 total in that axis. Still, of course it needs to be looked at, like every issue, on every vehicle. I'm not inside the valve issues they had, but I don't think this is related (the thrusters apparently fired, just not well enough, while the other valves were "welded" shut).
Yes, asking "Is this such a big deal?" is needed, otherwise you come home after any part fails.
I'm not selling CST-100 or defending Boeing here, but I'm sure things failed in Dragon and nobody is screaming "space disaster coming!!!". Didn't a Dragon blow up on the ground?
Redundancy is what brought CST-100 to 100m of the ISS and closing (apparently safely). Even the best designed systems fail, and when that happens in-flight, redundancy is all there is left.