Sounds like an LBS that has no clue how to tension and true a wheel properly.

Find a new LBS. One that builds wheels. 32h might be marginal for your weight, but 32h 3x laced should be fine if properly tensioned, stress relieved and trued, if you ride it gentle (no potholes and curb jumping! )

My mountain bike has 32h 3x wheels and has for 11 years (same set). I have weighed between 200 and 235 during that time, and they were NOT properly tensioned till about 3 years ago. I beat on them, jumped, rode rough anything a young 20's guy on a mountain bike can do. Sure I had to true them every so often using the brake pad to get them "close" but they have and continue to hold up. CR-18 rims (known to be strong) laced to Shimano LX hubs. Machine laced, $150 wheelset. I got them, tossed tires on them, and away I went.