Making changes on a new team

As a designer/developer on a new team, where I'm also the most experienced, but haven't been given the path to recommending change wherever necessary. In other words, I was brought on to be an individual contributor, not specifically a consultant, although it's very obvious in many places that the app lacked a designer, and that the code lacked senior developers. For context, they don't do JavaScript testing because "the team was new when we started and we wanted them to get off and running." So the question is how one can implement change, and be a useful consultant to make the product better for the user, but do so diplomatically. Or does one just do one's job and not make suggestions? Business and Engineering alignment