I've been teaching English since 2007 and in that time I have heard people say "It was delicious" about 34,600,000,000 times.
Yeah. It gets tiresome.
If you want to sound like a native speaker and maybe get a higher score in your IELTS test, you should bring some variety to your language. That means ditching "delicious" and using more descriptive words.
When talking about food and IELTS, you don't need to go looking for really rare words that few people use. Instead, just find some appropriate adjectives for the taste and texture of the food. In fact, I compiled a PPT with some of these words and you can see it here.
Sometimes you need to talk more specifically about food, such as answering this cue card about an unusual meal:
When that happens, you need to be able to think of an answer quickly and then talk descriptively about the food (or situation) in question.
Doing this isn't easy, but if you slowly learn food-related vocabulary for IELTS, then you will build up a good knowledge over time and be able to talk quite freely about unusual or regular meals.
If you have any questions about English or IELTS, drop them in the comments below and I will answer them for you.