Scale down an image in GIMP without losing resolution

How do I scale down an image to a smaller size in GIMP without an unnecessary loss of resolution? I know that I am losing too much image resolution because when I downscale the same image using HTML code and display it in a web browser I am getting a noticeably sharper resolution. By noticeably sharper I mean that details that were completely absent in the downscaled image in GIMP are displayed the way they should be in the web browser, and the difference in resolution is easily visible without zooming in on the image.

Original image

Downscaled image

I have already tried the answers to the following two questions, but none of the answers gave me the same image resolution that I am getting with my HTML code.

I am not looking for recommendations for web applications or services. I want to find a way to downscale images locally in my computer without an unnecessary loss of resolution.