Jürgen Hubert commented on Spelljammer by Jeff Grubb
I think one of the main flaws of the original #Spelljammer #dnd setting was that it tried to hard to be a sort of "connecting tissue" between other D&D settings, rather than having its own unique developed culture and environment.
While #Planescape also connected the different D&D worlds with each other, it went much further into being a fully-developed setting in its own right, and thus I regard it as the superior line.
If Spelljammer had published a collection of interconnected crystal spheres - a whole "space sector" for the PCs to explore, with different factions and cultures that play off against each other - then it might have been a lot more interesting. To me, at least - others might prefer the "toolkit" approach that Spelljammer ultimately took.