One of the tenets of material design seems to be that a rectangle should not reveal its true nature until you click on it. It might be a button, a text box, or just a rectangle!
Like, individual websites might do their own weird takes and have their own design systems which are mistaken for 'material design', but I don't think you can fault Google for making text boxes too similar to buttons.
Text fields https://m3.material.io/components/text-fields/overview - underlined or outlined, have their title text
Buttons https://m3.material.io/components/all-buttons - fully colored or outlined, may have a shadow, more rounded, differently-styled