Modernist describes that same clean, simple, man-made-material style of art and building — the one learner’s books often place in the 1940s to the 1960s. A modernist building might be a glass-and-steel box. A modernist chair might have a plastic seat and legs like sticks. As a noun, a modernist is a person who makes or believes in that style. So the word does two jobs: it names the look, and it names the people. It is a school-and-museum word, a little more technical than modern. Though actually, as with modernism, some teachers use modernist for an earlier break in art and writing, not only the later simple buildings. The sense you need here is the style of simple shapes and new materials. Do not use it when you only mean “up to date.” A modernist kitchen in a design book is a style choice; a “modern kitchen” in an advert might just mean new cabinets.