A certification gives you enough information not to kill yourself. Open water is not meant to make the student an expert. Perhaps at one time it was but not today. The diver is expected to continue their own education with experience and additional certifications. An open water certification is a "license to learn".
With a crappy, unethical instructor yes. But that goes against the RSTC and WRSTC guidelines and the guidelines of some agencies. They say an open-water diver should be able to plan, execute, and safely return from a dive with a buddy of equal training and no professional present. Immediately following the class, they should not have to use a DM or other dive pro to continue diving.
They should have a solid enough foundation that, over time, they can expand the places, conditions, and depths to which they can dive.
I never handed a student an open water card if I felt they could not do this. Some often chose to dive with DMs or guides when they went on vacation to see things they did not want to search for. There is nothing at all wrong with that.
But they also were fully capable of telling that DM or guide to sod off if they tried to take them somewhere they knew they were not ready for. And find their way back to the boat or shore on their own. I would not have given them a card if I thought they couldn't.
The "license to learn" phrase is a copout by instructors and shops that don't want to take the time or effort to give the students what they are paying for and then lie about how they need to take more classes.
It's just another reason I retired. Besides getting older, I'm sick of the unabashed greed and lack of morals and ethics in training.