Can merchandise over saturation also be a factor? You have at least three different scales of SW action figures competing with each other now.
It can be a factor, but since the toy sales are related to the search volume for Star Wars in general, I would say it is brand recognizability in general, where the saga films have been competing with the standalone films for the audience’s attention. The MCU get away with multiple standalone films, and cross-overs, because the films are interconnected. It might have been a better idea to finish the trilogy before introducing standalone films. The standalone films could have filled the hiatus between trilogies.