How do you remove interior faces? Here we have two overlapping cylinders:



They could be one mesh or two separate meshes. I don't care.

What I would like to get blender to do is remove the interior faces.



I'm having several problems.


Select > interior faces doesn't do anything
Many "answers" to this question tell you to press select while in edit mode but in 2.8 that's how you tell blender to start animating.
Boolean (Intersect|Union|Difference) (assuming the cylinders are two separate meshes, of course) doesn't work and it often generates strange geometry. How you get this out of two circles is beyond me. In the image both cylinders have the same height but usually I have to make one cylinder taller so that it's above and below the other cylinder to get it to work.


 

Am I making a reasonable request here? For more context, this is the mesh that I would like to clean up the interior of. 



The cylinders are just because I've given up doing this with more complicated meshes. How can I remove as many of the vertices/faces from the inside of this mesh as possible? Thank you.
You're making it very complicated, there are several ways to make your object, the simplest would be to bevel the angles of a rectangle. Then you may need to work the topology but it depends on your final goal.