3. The apple pie was insipid. The cook forgot the spices. (Note that this cook is not insane, just forgetful)
4. The apple pie was distasteful, repugnant, repellent, vapid, flat, flavorless, dull, wishy-washy, inane, jejune, banal. The cook consulted Merriam-Webster's Dictionary of Synonyms and Google/define tool.
'Google/define tool'-- I just did a quick search for this and couldn't find it, Elena. Could you tell me where it is and how you work it for synonyms/antonyms?
This says the antonyms of "delicious" are; distasteful, gross, unappetizing, unsavory, yucky. Personally (as an English learner) I have memorized only "distasteful" and "unsavory" as the antonyms of "delicious".
Not all the apparent antonyms would work in every context.
For instance, 'delicious!' is used (by some people) as a very positive remark on tasting a particular dish.
For the 'opposite' in such contexts, you would need an equally forceful negative remark. 'How unsavoury!' would be quite mild, for instance; though 'Yuk!' or 'Gross!' would probably do.
Where are you from, Mr. P, that "not bad" is "praise enough"? From one of those O-U-R countries, where it takes a little more effort to produce flavour and colour?!