To be fair, this was written in 1986, so Batman and the JSA weren't actually in the same continuity at the time. (Would have either come out during, or too close after Crisis for the changes made to have an effect.) So, only 2/3 of those are actually MISSING.
However, the Titans and most of the rest of the JLA being missing are big points - only Superman is mentioned, and only the Flashes are explicable, given the circumstances at the time of writing (at the time, Barry was missing and Wally was enough of an emotional and physical wreck that he could have ended up permanently out of the game, instead of taking Barry's place). But then there's Wondie, the Lanterns, the non-Robin/Flash Titans, Green gods-be-damned Arrow, for flip's sake. There's no reason for all of them to be out of the game. Hal and Ollie, particularly, I don't buy the 'they were outlawed!' part. Hard Travelling Heroes was still a fresh memory at this point, and that Hal and Ollie - well, any post O'Neil Ollie, but that Hal - I can see being 'screw the rules, I have green clotheswhat's right on my side'.
It makes sense, from a writing standpoint that Miller would ignore them - his story doesn't work if they're still on the beat, and only a handful of them can be plausibly explained (and I don't buy his explanation for Superman, which is another problem I have with it - while the Post-Crisis Superman is 'mine', I don't buy it for the pre-Crisis, either) as out of it, so he just ignores them.
Which is a problem in itself, since there are too many things that suggest this isn't a world that was ever lacking in heroes.