First off, The whole idea of the dragon balls getting collected else earth gets destroyed by the energy of the wish was done with the ultimate shenron in the first arc.
Also the whole but it's cool cause their evil versions of shenlong which a is not technically true but even assuming so wouldt that just be really unoriginal considering every other major villain are evil versions of another character in some sense eg baby vegeta and super 17
not only that but their pretty bland all having no unique traits or personality say for nova shenron and even then, he's not even a bad guy in this arc.
Also the whole but it's cool cause their evil versions of shenlong which a is not technically true but even assuming so wouldt that just be really unoriginal considering every other major villain are evil versions of another character in some sense eg baby vegeta and super 17
not only that but their pretty bland all having no unique traits or personality say for nova shenron and even then, he's not even a bad guy in this arc.