We would all like to answer Yes or No, and a lot of us would have good reasons to do so, but at the end of the day, it depends on the company, budgets and a lot of other factors.

Some companies lose tons of money and wrongfully divert valuable company resources by "improving" their internal application ux. Even if you know you should, you are still faced with the question of how.

The only thing that can be said with any certainty is, that internal applications need to be analyzed for productivity, and if that analysis comes out with results that say "if we make these changes, we will see this improvement of productivity", and those numbers are worth it to the company, then they should be made. If you can't come up with a convincing, detail reason why a feature should be changed, then it shouldn't be done at all.

In a perfect world with unlimited budgets, Yes, improving ux for your internal employees is going to raise moral and productivity. If you make the internal application ux like playing an Xbox you may even get people to work long hours for lower wages.

If we think about this in a war analogy, you'd get a lot less pundits for solid Yes or No answers. Should we reinforce the fort, or charge the enemies fort? Now you'll begin to see how information and analysis should be used to determine what the next step is.

Also, on the end of every feature change is a person who writes the checks, and will only be motivated by clear reasons, usually ones that will benefit monetarily beyond the costs.