How can I fix this very noticeable patch job on my bathroom wall?

I’d guess there are 3 things going on here. The texture of the surface, the sheen of the paint and the repair itself. If you can try a matt or flat paint , you can even buy a sample and test just that area. If you must use the semigloss, try putting a piece of cellophane on the area while it’s wet and then pulling it off quickly to replicate the texture. Otherwise have the repair done by a professional drywaller, prime it (if you didn’t in the first place) and finish with the semigloss.

Home Depot sell Homax texture in a can and it works very well. First things first. You need to sand down that spot, then spray with the texture. Then prime the spot with Kilz. The reason for this is to get an even coat. Unprimed it will shine like a beacon as you said. After all is dry, you can paint with whatever sheen you need.

Also you can take out the molly in the wall and fill with dap and treat it the same way as the other spot.

Just a note, the shinier the surface shows more flaws. , flat hides flaws. That's why builders usually only paint with flat paint on walls and charge extra for the satin washable sheen.

Flat may hide flaws, but it's a disaster waiting to happen in a bathroom. Consider what gets splashed on the walls every day. If you can replicate that texture, do it. Then paint with semi-gloss paint, not gloss, not eggshell, not satin, not flat. You can scrub the 'flatness' off the wall over time. The reason the patch shows up so much right now is that you have patched it, and it is now a different sheen.

I'm thinking that the repair was never properly primed prior to painting. Not priming will make it a BEACON for your eyes. I'd sand it down, try to replicate the texture as best you can and then prime with 2 coats. Finish with your wall paint.

If it is still bothering you, relocate the towel bar so towels cover it up.

It looks like the wall has "orange peel" texture. Take your up-close picture to Lowes, Home Depot or your local hardware store to check exactly what texture it if for sure. We have used both the extremely smelly and the low smell products with good results in our Florida bathrooms. We sanded the area, enlarging it a bit and played till until the patch disappeared. It was also helpful to paint the whole wall where the patch is, no need to repaint the whole room. It was a learning curve but we are now pretty good at dealing with the textures of Florida walls.

Robyn Garner has it right. The patch was poorly done and not primed. Follow Robyn's advice and your patch will disappear.

First you need to sand that place down as smooth as you can get it. Take a look at it and see how it looks after that. Wipe it off and look at it again. If it looks like it's now smooth you move on from that and paint it.

Make a feature of it! Add a Picture or a mirror or shelving, or cabinet etc.