There has been a shift from complex attacks to simple attacks using cars and bladed weapons. Complex attacks can be quite effective, but because there are multiple attackers, they have firearms, they require safe houses and a support network, complex attacks often leave a trail of evidence that jeopardizes the network of support relationships. You can see this in France and Belgium, where press reporting on attacks over the past several years (examples: the attack at Charlie Hebdo, and then the Bataclan attack) indicates there were post-attack investigations and then related arrests.
In contrast, simple attacks using cars or trucks or bladed weapons are almost impossible to stop and the person can even be misidentified as unstable, or criminal, instead of a terrorist. The simple attacks can be done with little planning by one or two people, which makes the old press reporting about "chatter" before an attack a thing of the past.
