I don’t think Figma is a tool to modify pixels. It is a tool to create digital products like websites, mobile apps, or any same thing. So if you want to remove a text on a pixel (image—jpg, png, etc.), then you would need a tool like Photoshop which is an image editor.
Edit: You can try suggesting that feature, though not sure how they’ll respond to it.
You can use a Slice tool, add 1x export setting, copy as png, paste and move the object to cover something up.
Or duplicate the image and use a mask that you draw with the pen tool for more precise shape.