Not really liking the round mirror. It looks proportionally odd with what appears to be the round? sink. I would go with a rectangular mirror and lights on either side. If you stay with the light above the rectangular mirror, find something more modern. What’s there now looks very dated and definitely needs to be replaced. Couldn’t the vanity be painted? Otherwise you have a pretty blank slate to work with. Look at bathroom photos on Houzz and decide on the color ways you like. Keeping the shower surround, I assume, so focus on a shower curtain and towel and rug(?) colors that work with your flooring and vanity top. Or you could change the vanity top to a simpler more neutral granite or whatever. Wall paint is easy to change.

A bigger mirror and 3-light sconce would go a long way to making the space more inviting.

Wallpaper would add color ... lots of great vinyl wallpapers available these days.

I’d replace the dark vanity cabinet with a warm cream one that complements the countertop. Then I’d choose a larger mirror and a simple, minimalist light fixture centered above it.

A framed print above the toilet, beside the mirror, would give you a lovely focal point as you walk in. I’d pick up a couple of colors from the artwork in the shower curtain and towels to bring everything together.

Since the open door blocks the towel-bar wall, I’d keep that area simple and just replace the towel bar with one in the same finish as the light fixture.

If you hate the dark cabinets and counter, start there, they're what's dragging the room down. Painting the cabinets a soft sage or cream and swapping the counter for something lighter will completely change the feel without having to move any plumbing. That fits the cottage blend much better than the current dark setup.

Emily's rendering is lovely!