Alternatives to "this doesn't add any value to that"

What are alternative ways to express that something that was added to a thing doesn't add any value to it?

You could say:

The Thing contributes nothing of use/value to That.

or maybe:

The Thing provides no benefit to That.

You could say it's superfluous, or surplus to requirements.

There's an idiom which captures the meaning. It is: 'to gild the lily'

However, use with caution as it just doesn't mean that "something that was added to a thing didn't add any value to it". It sometimes, is also interpreted as: " that something also made something beautiful worse in trying to make it better."

The other term commonly used in lean manufacturing is muda. Muda (un-usefulness) is one of three types of waste which are recognized in lean manufacturing; the other two are mura (unevenness) and muri (unreasonableness).

The phrase bells and whistles refers to superficially attractive elements which are non-essential or non-differentiating, especially in items which compete on multiple features (e.g. software, finished goods, excursions, even compensation packages):

The redesign doesn't address the flashlight's weak bulb or flimsy switch. It merely adds a clock that displays Greenwich time and a third case color, and other bells and whistles.

This phrase has been particularly popularized since the rise of consumer electronics, but English has many colorful words for superfluous ornamentation or decoration: frills, or more informally, doodads, jazz, gewgaws, falderol, or gimcrackery for example.