I never got any direct placements from Broadjam, but my music was selected by a bunch of library owners that I still work with to this day. And those libraries do get my songs placed. So the opportunity is there.
That said, none of those sites guarantee anything, except that you will have the chance to pitch your music. You're going to be in a group of sometimes hundreds of other musicians, just from one of those sites, all going for the same placement. And of those hundreds, many will offer professional-grade music. If there are submission fees, those with more money to spend will submit more tracks. Just a few examples of how competitive those sites can be. But overall, there are people who have various levels of success with those services.