What are the disadvantages of a Mediterranean diet?

I could never go full veggie or vegan but with the hot weather I have been eating lighter meals lately and I have to confess I have enjoyed it.

Mainly I've been having salad and grains like cous cous, quinoa or rice, lentils with smoked salmon or mackeral, plus olives, avocado, tomatoes... it makes such a difference after I've eaten to be 'satisfied' and not hungry anymore, but not full or stuffed or sluggish.

Anyone who eats this way could they point me to more recipes or foods and tell me any downsides? With the fish I am guessing it would make me unpopular in the office 🤣

I have read a lot that oily fish, olives etc are 'good for you' but what is the reason? 🤔