Opposite words for spicy:
dull, prudish, nice, stale, correct, vapid, respectable, prim, victorian, genteel, insipid, tasteless, nonobscene, puritanical, prosy, decent, seemly, clean, proper, unsexy, straitlaced, polite, cold, g-rated, staid, stupid, innocuous, decorous, priggish, flavorless, flat, inoffensive.
Usage samples:
  1. His comments on our news were always much more spirituels than the best of bons- mots we could impart, and frequently a good deal more spicy than our versions of Parisian doings.
    "Fragments of an Autobiography", Felix Moscheles.
  2. Puffs of sweet, strong, spicy steam rose out of it as they jerked it this way and that.
    "Harding's luck", E. [Edith] Nesbit.
  3. The dark tiny leaves of the creeping snow- berry were all sprinkled over with delicate drops of spicy foam.
    "Little Rivers A Book Of Essays In Profitable Idleness", Henry van Dyke.
  4. " But the gingerbread isn't burned at all," volunteered Susie with satisfaction, after a keen and anxious scrutiny of the spicy loaf half- way out of the oven.
    "Tabitha's Vacation", Ruth Alberta Brown.