Cheap stems are rad. They do just fine holding the handlebar in place and come in many sizes. Most are even lightweight. What’s the problem? Tolerances.
Most cheap stems are cast or use cast parts in a weldement. These parts have deviations that cause a problem. The issue is that the bottom side of the stem, the headset side, must be a plane normal to the steering axis for the headset to work well and the stem to stay in place. Most cheap stems are very bad about this, some are horrific. It’s a good thing that this can be fixed.
Make a 1.125″ arbor for a lathe and trim the face. Simple, but a major tuning job often neglected by bike shop staff.
Now my $20 stem works as well as a $100 stem.