Most tidal I am familiar with capable of generating anything approaching reasonable amounts causes significant ecosystem impacts- you basically replace entire shorelines with concrete bunkers that act as a crappy gravity battery (you can get significant mass from the water, but not much lift from the tide).

I think most research is focused on utilizing less unique space- rooftops, open plains, open ocean. Shorelines are tiny spaces for how ecologically unique they are, plus they tend to be highly desirable for other human uses as well.