That is fairly normal. Supports on an FDM printer cannot support the entire surface very well and still have it break away.
Washable support structures is another means, but there too, you are dependent on how the slicer treats supports.
With washable support material, I would have to make a negative part and place that below the real part.
I am not sure of any slicer that would handle that for me. For the masses, MeshMixer is a nice free editor to help create such things.

Of course, you can try changing the orientation of the part but other artifacts will be seen.

This is the problem with 90% of what you find on thingiverse... it just isn't designed to just push print and have it be 100%.
When I find a figure that has half a chance, I print them. Even then I learn of things that will fail.

There are solutions... they just are not easy to implement in all cases.