What is the word for using one word to replace another for cosmetic reasons?

Solution 1:

"Despite the superficial changes," works well in this context. Two related definitions from Oxford: "Existing or occurring at or on the surface," and "Appearing to be true or real only until examined more closely."

To insinuate that the revision is a pretext, the ostensible or so-called changes. Also disparaging, but without the implication of dishonesty: trivial, unimportant or desultory¹. If you approve of them, stylistic changes make something sound better and clarifying revisions (or, more commonly, clarifications) make it clearer, without altering the meaning. Some more neutral options include minor, incidental, inconsequential and negligible.

¹ Which have different shades of meaning: trivial changes don't affect anything because they're so minor, unimportant ones changed something that doesn't matter, and desultory ones have no focus or purpose.

Solution 2:

Cosmetic is fine. It's often used in this way, cosmetic changes: changes that may appear interesting but lack substance. Another term is aesthetic changes: changes in appearance, perception. Another relevant expression is lipstick on a pig: when one tries to make something ugly appear nice by some superficial measure, but obviously without success.

P.S. I agree with Davislor that words like superficial and inconsequential are good words to describe changes that don't really change much; but those words don't capture the question's desire for a word to describe changes that make it "appear better". Even so, they may fit the desired context.