"Lets say you wondered about the pros and cons of a certain vaccine (actual reports of harm/reactions vs the risks from the illness it maybe prevents). A straight search engine would give you results that are directly related to what you want, perhaps weighted by page popularity."
The current situation is not so different from your "straight search engine," but the result is slightly dystopian. Search engines, and online profiling, try to give you more of what they predict you want. If you're searching for "vaccination risks" then you'll tend to see results that were preferred by people who have fears about vaccination. Those results might skew more towards the infowars end of things rather than NIH or WHO or NEJM sources.
Search engines take our confirmation bias as input and attempt to satisfy it.