lackluster
underbrained
not the sharpest knife in the drawer
not the sharpest tool in the box
not the sharpest tool in the shed
vacancy
inadequacy
unintelligence
stupid
unbright
unintelligent
untalented
ungenius
stupidass
nontalent
halfwit
vacuous
vacant
mindless
rude
slow-witted
skillessness
ungifted
gormless
simple-mindedly
hopeless
naive
talentless
inexpertness
talentlessness
dim
light-witted
shallow
ham-fisted
lustreless
lacklustre
fumbling
untalentedness
underwitted
unskillfulness
lusterless
incompetent
nonintelligent
bungling
clumsy
strengthlessness
unskill
half-witted
nonsavvy
dull
unimposing
qualitiless
feeble-minded
unsophisticated
simpleton
simple
undertalented
unknowledgeable
bad
dyscompetence
mentally challenged
lightweight
unworldly
unartful
insufficiency
weak
unskilfulness
nonintelligence
short-witted
stun
ambitionlessness
qualitylessness
naïveté
unrenown
inexpert
indocible
skilless
belated
unable
nonintellectual
acognitive
improficiency
nonproficiency
unproficiency
cloistered
half-brained
intellectually challenged
uninventiveness
cerebrally challenged