When describing food, 'insipid' implies it's so lacking in flavor it doesn't stimulate the senses. Not just mildly bland. Even with salt, the insipid stew failed to please our palates.
Pro Tip 2/3
Negative Connotation
'Insipid' often carries a negative feeling, suggesting disappointment or dissatisfaction with a lack of taste. The chef's new recipe was sadly insipid, falling below everyone's expectations.
Pro Tip 3/3
Mildly Polite Criticism
Use 'insipid' to diplomatically criticize food when you want to be kinder than saying 'bad' or 'awful'. Your cake is a bit insipid, but I appreciate the effort you put into baking it.