Loving this show. More surprisingly my wife also loves it so it's doing something right. It has a fantastic cameo in episode five and there is also a great pay off from episode four with a significant plot twist that in hindsight I should have seen coming. I really like the series as its a collection of flawed characters each jostling for their place in any entirely impossible environment.
I honestly don't recognize the negative reviews? The show Wrecked never aired in the UK so cannot comment on which is the best desert island show, but its not a unique concept, Swiss Army Man, Cast Away, Lost all the way back to Robinson Crusoe. FWIW Marc Wootton also created a show called La La Land about people trying to make it in LA but add singing + love and the movie version is not called a copied concept.
Brett is meant to be laughed at because of the tropes as much as the lines his delivers, he is not meant to be an actual representation of a realistic gay person anymore than Harriet a realistic head teacher, or Susan an actual religious person, they are funny fictional characters brought to life for our entertainment, and entertain me they did!