We use several tools, but plagiarists also use them too, and it can take a keen eye to spot some writing that has been copied and paraphrased just enough to evade detection by these apps.
We work on suspect articles co-operatively. Having a strong editorial team available around the clock helps. One of us spots something that doesn't seem quite right, posts it on the Slack channel, and others weigh in.
Sometimes it's legitimate - the writer might have another gig on a blog, or contributes to Quora or something - so we don't want to go off half-cocked. I usually ask for an explanation, unless it's something really blatant, like the guy we had copying poems directly from Rumi, who has been dead for centuries. No explaining that away!
Yes, the apps pick up a lot, and some plagiarists are just lazy. Others are morte inventive and I often wish they would apply their brainpower to writing original material instead of wasting everybody's time in thinking up ways to fool the system!