The problem with Kiruv is generally they are unsuccessful, very few non-relgious really want to be frum. Some want some connection with Judaism and people mistake that with wanting to be frum. Especially because many people have lives that make it almost impossible to be frum (Like they are married to a non-jew or have non-jewish children or non-jewish parents) . Many people might want to go to Shul once a week and maybe learn about some judaism, but that all they want
The only reason chabad is a bit more successful is they are willing to look the other way and dont demand total compliance, So they consider someone who drives to shul every shabbos a success story (They do not condone such behavior, they look the other way and maybe say that its wrong to do so in a nice way, but they do not fire and brimstone them)
Also generally Chabad Rabbis (and their wives) are much more open and friendlier than other rabbis so they can get more people