Yes, once a lobster gets too big or old it is inedible................
We were on a very small, high-end cruise last year - the final night the choice was either lobster or filet mignon. I ordered the lobster - and it was terrible, old, rubbery and smelled fishy. Very disappointing.
We went on the same cruise line this year - and I knew this time to order the beef - it was thinly sliced, served with a nice sauce over mashed potatoes - and absolutely delicious.