Most shmups are pretty much the epitome of "gameplay over story".
For most shmups, the plot is All There in the Manual aside from the ending cutscene.
Mind you, this is primarily because they're arcade games, and, well, you know, there's probably going to be a line...
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Speaking of which, it seems the reason the ALLTYNEX kickstarter has been losing funds is because people are withdrawing their donations, since they don't think it'll reach the stretch goals.
Which is dumb. They're dumb. Obvious self-fulfilling prophecy mentality.