Facebook can still show relevant ads without showing personalized ones. For example, if there is a facebook group about car restoration it doesn't take a genius to guess what kinds of ads members might be interested in.
Personalized ads mean they make a ton of assumptions about you using incomplete and inaccurate data. If you actually value advertising as a means of discovery, why would you want your exposure to new things limited to only what marketers think you should be interested in based on stereotypes, or flawed assumptions?
Relevant ads are better because there are fewer assumptions being made. Whatever content you're engaging in dictates what you see, not market research and guesses about who you are.