Subsurf ruining seemingly clean topology? Here’s the mesh.



Here’s it with subsurf.



So, why is this happening? I went out of my way to manually join the mesh as to create quads. Sure, it’s a funny shape. I can see how the right angle kind of looks whack, but conceptually, it’s all quads, right? I want to know the technical reason it’s not smoothing this over if possible and means to achieve this if this is not the correct way to go about it.

Note that:

1) I deleted the inside faces
2) I merged by distance

Thank you,

John
You need to add some "loop cuts" and slide them close to the edges where your mesh is joined. You may also have some z-fighting going on. Meaning faces that are occupying the same space.