assuming you indeed are using util correctly (doubtful) and know how to hold angles (doubtful) then logically your biggest issue would be positioning, movement, and aim. maybe econ/ult management too.
winning dms doesn't necessarily mean anything btw
focus on getting better movement (do I walk here? how do I swing this guy? where should I path towards when taking/retaking site? how do I make sure that I get the best possible gunfight after repositioning?)
knowing where you're positioned on the map (am I in a spot where I can leave after getting a kill? am I positioned so that somebody is watching my back or that nobody can shoot me from behind? am I ready if someone clears the spot I'm in or am I willing to get my one and done to win the round? am I ready to swing/peek off someone's util or am I looking at spots other people are looking at/have cleared/have already used util on?)
aim is more difficult, but (am I keeping my crosshair on the best possible angle? am I ready to take a fight whenever I move my crosshair off an angle? am I clearing things properly? is my preaim good? am I already expecting where the enemy will swing from? am I ready to swing close, swing wide, or try and move back to get a better angle?)
if these things end up being wrong, reassess after you die and try to make sure you don't make that mistake the next time.