I think the number of times ships have to miss Grand Cayman is over-stated. I think in probably 10 cruises where it was on our itinerary, we missed it once.
When it does happen you hear about it, because it affects all the ships visiting there that day. Yet, how often do we hear about it happening? Answer - infrequently. (They have announced they are dredging the port, to build a pier, to eliminate tendering)
I also don't think tendering there is as big an issue as Trip makes out. Sure, for people with mobility problems, tendering anywhere is going to be somewhat of an issue.
Depending on where it is on your itinerary will be the deciding factor for if you get a sea day, or a replacement port of call. If the ship is on it's return to leg to Florida, often the ship will head to Nassau. (I'd rather have the extra sea day).