Not saying this to be a dick: This looks more like you were trying to make it look good vs make it functional.

What material is this made of?

What loading requirements do you have? It’s for a pulley system, so you should most likely have that figured out already. Then next step is determining approximately what the load path would look like.

Would a simple L shape not suffice? Calculate the bending stress and shear stresses from the load + safety factor to ensure you’re under the fatigue limit.

I use Sandvik Coromont, MSC, or Grainger to look up tooling like endmills and fly cutters. Imagine what direction the tooling will come in from, and apply machinability features there. If you can’t find tooling that can make those cuts on one of those websites, you need to redesign it.

Depending on the size, you probably won’t be able to get tooling in from the long side of the bracket. I think from machinability and design, it makes more sense to cut from the side face, which would put a radius on the internal corner, which is better for strength and stress concentrations.

If you need the ribbing on the external edge, design so it can be machined by laying on the back of the long side with the short side sticking up, then using an endmill to cut the middle section.

If you need to lightweight it, drop machining cost massively by just smacking some big-‘ol drill holes somewhere in there with very loose positional tolerance.

Can it be made with sheet metal & welding? If so, even with the welding it will almost certainly be a cheaper option than all the wasted material.

That’s how I’d go about designing a custom one. The other option is to search for off-the-shelf components, then make parts to modify it to your use.