Yes, they are money grabbing (#_)%#(*#Y@. However, they do have real information, too, if you have the patience to wade the muck. 10-20 years ago, all of this information was a painful rootsweb search of disjointed garble. If you were lucky and descended from a Mormon ancestor, you could fight the Microfiche upstream for snipits. Ancestry came along with a better user interface, a built-in gedcom file maker, and connected databases. It was a homespun dream for those of us who cannot journey to larger genealogical repositories. It was also very heady to be able to "copy" the family tree records of those who seemed to have it.
Even though my genealogical mentor warned me to source every person at least 3 times from the best records around, I ran through the Ancestry fields like a hungry sheeple, taking everything I could. When the dust cleared, I had a tree filled with people who either didn't exist, or existed, but were not actually related. I moved to a gedcom program on my personal computer and started over again. At least not everyone in the first 4 generations was wrong. It has been a long battle uphill, though. Now, I drill down and source things. I also joined WikiTree. I prefer a more academic approach, as this is really at its core history which requires other eyes to check our work.
So, yeah, but go slowly, save everything on your hard drive, multiple sources, and stay away from "WorldTree" sources.