insipid

Lacking flavor or zest; not tasty.

Lacking qualities that excite, stimulate, or interest; dull.

Without any taste; not exciting the sense of taste; without flavor or savor.

Without a definite taste; having a taste which from its faintness and undecided character appears negative, insufficient, or slightly disagreeable; flat in taste.

Hence Without power to excite interest or emotion; without attraction; uninteresting; dull; flat.