Someone just recently told me that while most people go to shadchanim, most people don’t end up getting married through a shadchan.
I don’t know if it’s true or not, and as Meno pointed out, it might depend which people. I would guess that people who are well-connected are more likely to be set up by people they know.
Going to a shadchan is hishtadlus. According to the Sifrei mussar, when you do hishtadlus, it doesn’t necessarily mean that Hashem will bring your yeshua directly through your hishtadlus. Hashem won’t bring your yeshua unless you do your hishtadlus, but He might not bring it directly through your hishtadlus. The only criteria is that the hishtadlus must be reasonable.
It seems to me that going to at least one or two or three shadchanim is reasonable hishtadlus, and then one can leave it up to Hashem to send your zivug through whatever means He chooses. (you may also need other means of hishtadlus as well.)