I agree with the previous two posters here, weather is always a consideration when one travels, when voyaging or otherwise. Inclement weather should not be a factor in a cruise rating or ship rating, unless the ship design is deficient and subjects voyagers to a rougher ride than would otherwise be the case under given conditions.
Missed ports are common, on an average three week cruise, for us, we usually expect to miss about two. Tendering is pretty common if one wants to visit out of the way ports in exotic locations or those not in the mainstream of ocean going freight transport. As you appear to recognize, a tender port is more dicey to navigate than a dock port, therefore aborted visits are more likely there. Cruise lines almost always bend over backward to find a birth at ports since it is much more economical for their overall operation if they can, it is not a case of them being too tight to pay the port fees. Some ports do not have the channel depth to accommodate large vessels while others simply cannot afford to build docks the size necessary to handle big ships.
You were fortunate to get into St. John's, a goodly percentage of vessels have to bypass St Johns due to weather, usually wind, fog or both. This is due to the very narrow channel leading into that port. We were on the Regal just days before you were and did make it into St Johns as well. It was the largest vessel to ever port there and they gave us quite a celebration because of that. A year ago we were on the Regal's sister, the Royal, and had to bypass St Johns due to 65 knot gusts at the port. During this voyage on the Regal, we found the North Atlantic all but a mill pond. Last year on the Royal we not only experienced 65 knot gusts for a couple of days but also over 20 foot seas. She handled them well, unless one looked outside there was almost no way of knowing we were in a "blow" except for the bow pounding on occasion.