Scott ignored his own style set in his original film; one of the unique elements that Alien had was its idea that the future wasn't some glamorous place with shiny starships, but a place where many of today's problems still exist; bad machinery and wage issues. One of the elements that Alien: Isolation will have is the retro-technology look that the first film had, but Prometheus is the opposite of that and features that bright shiny future that is so unlike the Alien films. This is a small detail, true, but it's the small details that show how much the director cares about the film.
Movies like Terminator 3 and 4 and Silent Hill: Revelation failed because the new directors didn't care about the themes nor the symbolism present in the previous films and therefore created a new film that was completely lacking in those areas. This is what Ridley Scott did with Prometheus; he set a dark and rusty world in Alien and then proceeded to take it away in Prometheus. This shows that either 1) he did even care for his original work enough to realize he was doing this or 2) he did realize this but chose to sacrifice the older look for a newer one to entice a wider audience rather than appease his longtime fans.