Why did you need to change the derailleur on a new-ish bike, and did the old one work right? If their was a problem like a bent hanger or cable friction swapping derailleurs will not alleviate the problem. Perhaps the Altus derailleur is more tolerant of mis-adjustment

I wonder if the shop did not route the shift wire the right direction around the anchor screw. It needs to go over the little tab next to the screw. If routed the wrong way it changes the lever arm length which affects the shifter movement per cable pull.