I’m not familiar with Samsung, but a couple of things to consider:
does your model have an internal filter or screens? If so find them and clean them
pull the sprayer arms and inspect the water ports. Sometimes gunk or hard food debris clogs them. You can clean them out with a toothpick and some shaking
get a dishwasher cleaner pack and run it on the sanitize cycle. *Alternatively get some citric acid powder and run a few cycles with that inside the tub.
It’s disappointing to hear a repair person say “get a new one.” My last dishwasher was 20 years old. I repaired damn near everything on it myself including the control board.