The layout of the house is a little confusing. There are two bathrooms connected to the master bedroom. The main bathroom above, and another small bathroom with a stand-up shower. This small bathroom is also connected to the living room. We intend to block off access to the 2nd bathroom from the bedroom and make it only accessible from living room. This is the thought process around updating the master bath to include a walk-in shower and generally make it more modern and fresh.

Something about the paint on the walls isn't doing it for me.. Maybe paint the walls darker, paint cabinets?

https://designerdrains.com/tips/8-simple-bathroom-design-tips/

Leave it as is and price it right. This Is not an inexpensive change.

Once you explained the layout, this makes more sense to me. Personally only having a small stand up shower would be a deal breaker for me (if I couldn't Reno myself). So making the change to get rid of the weird two bath setup could make the home more likely to sell to people who don't have the imagination or the time for a Reno. You might sell quicker, but you probably won't actually make the money back. I think it's generally best to let the new homeowners decide what they want and just price your home accordingly.
I wouldn't replace the vanity. It's not really that big a bonus for potential buyers, relative to expense. They should have no pronlem swapping it themselves if they care.

Forget the remodel, pay a professional stager to stage the house and put it on the market....the bath looks pretty good, and you will move on faster with a quick sale.....Studies show staged houses sell faster and for more money.