Hi @AndyYang,
What you can do to have the labels on top (of all layers). I did something similar with wheel/edges symbols which I published as a map image layer to show certain status on data in related tables.
left: the wheel symbols are only visible when no other features are blocking
right: the wheel symbols are visible
1. vector tile layer: ' Move to the basemap'
2. then, choose 'Set as Reference Layer'