I still maintain that the alien mcguffin could have worked in 4 just as well as the religious mcguffins in 1-3 if the movie wasn't such a George Lucas-dominated CGI fest.
Like I think the concept on paper was fine, but because no one had the energy or willingness to challenge a prequel-era George Lucas mad with power, it turned into... a trek though a CGI jungle to save a CGI alien who eye-humps Cate Blanchett until she turns to CGI dust.