> If algorithmic theorists don't care about practical performance then why should we care about what they're doing? It's just a strange game they're playing, of no interest to anyone else.

You don't need to care. But every so often breakthroughs in theory can be turned into breakthroughs in practice.

> It seems like rather than coming up with more "galactic" algorithms, a more useful thing to do might be to come up with a replacement for big-O that's not so exploitable, and to convince theoreticians to play that game instead.

There's plenty of replacements.

Btw, we already have the optimal (in big-O terms) algorithm for every NP hard problem. We just don't know whether it runs in polynomial time or takes longer. And, yes, that algorithm called Levin's Universal Search is a galactic algorithm. Simplifying a lot, Levin's Universal Search does some clever interleaving to essentially try all possible algorithms in sort-of parallel.

Lo and behold, even the theorists you complain about don't see that 'loophole' as a solution, declare victory and go home. They still keep researching.