Oh I'd agree that they're often bad as setting policy.  And following it.  No better example of the latter than the existence of 11M+ illegal aliens in this country.

On illegal immigration, we have good policy but horrible implementation.  On legal immigration is kinda the opposite -- we have good implementation but IMO the policy needs to be tweaked to lower the limits for the number we allow in.  We simply don't need to import millions more people.  We're having enough trouble supporting the 320M we already have without lowering our standard of living and further straining our natural resources.