Using a MeshCollider for a tile-based 2d sidescroller terrain collisions

I've been working on a 2D engine similar to Terraria's, I have chunks composed of a set amount of blocks and render them using a single mesh for better performance. My problem is that I'm having a hard time handling collisions, since each chunk can have pretty much any possible array of blocks (think of scattered blocks across the chunk as the worst case scenario). I've tried using an EdgeCollider to handle this but it has proven to be a very complex solution, so I've been trying something else, like using a mesh collider for this.

The problem that comes when using the mesh collider is that I have to start working with 3D physics, which is fine, I'm ok with that, but the problem is that now I have a cube (a movable entity that is supossed to be able to land on the floor) that needs to be able to collide with a planar mesh collider that is facing the camera, but this just gives weird physics glitches and thus is not very useful to me.

I've tried extruding the MeshCollider but without a lightweight method of not extruding the internal triangles this becomes already to heavy for my needs.

I would really appreciate if someone that has dealt with a similar problem can help me find a solution. I'm basically trying to build my own Terria-like engine, and I've already read this post which was actually extremely helpful, but sadly there isn't much info about how the collision was handled and I think that I might be overcomplicating things a bit.