No, high-frequency trading is not good for the economy, for high-frequency trading violates equal access to trade and thus a blatant violation of equal access to freedom. And an economy that violates the principles of freedom is quite the opposite of free and prosperous. It is implicitly oligarchically controlled with the devastating consequences we now face every day.
I hate to burst your bubble, but our stock markets are not free-market systems. And as Goethe says, “None are more hopelessly enslaved than those who falsely believe they are free.” And so, all those without access to high-speed trading are hopelessly enslaved to those who do.