I need to see the Pax from further back to get any idea of what you can do . Why did you choose to not remove the baseboard and snug this up to the wall? I can't imagine what a shelf above the wardrobe would accomplish but I need better pics.

It appears, that the unit is sitting crooked. It may be the floor that is off, rather than the wall. Remove the unit, remove the baseboards, and then use shims at the bottom, to get it all up level with the wall, and screw it into the wall studs You can then use a baseboard along the bottom to hide the shims.

I can see that cutting away the baseboard to snug the cabinet against the wall would not have worked, as then the door would bind against the baseboard when you opened it.

What I would do is go back to IKEA and buy a matching door to scribe and cut to conform to the contours of the wall and baseboard, i.e., a filler piece. As I did here (in this case the filler is a piece of primed MDF painted to match the doors):

Custom-Fitted IKEA Pax Wardrobe Cabinetry · More Info

yes, that is what our contractor did with our Pax, got a piece of matching white and used it as a filler.

Because you have a sloped ceiling, it complicates trim issues and how it would look after taking this approach. It also looks like the wall and/or floor are off, which gives you a gap of increasing width as you go up the wall. This is accentuated by how close you've situated the unit to the wall. If it were me, I wouldn't try the trim option: it would be pricy to do it right and it might not even look good because the sides would need some kind of pie-shaped piece and the filler piece across the top would be rather high.

If it were me, I'd embrace it as a piece of standalone furniture, but move it over to the left a bit so that the spacing issue between the wall and the right side wouldn't be noticeable.

These are are very helpful suggestions. Thank you!