to make superficial changes without altering the essential content; to change the form but not the substance; old wine in new bottles.
这家公司虽然推出了新产品系列，但仔细一看，核心技术和功能与老款并无二致，真是换汤不换药啊。
Although this company launched a new product line, a closer look reveals that the core technology and functions are no different from the old models; it's truly a case of changing the soup but not the medicine.
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