Glass' is talking about good taste by your own standards, and standards that are higher than you can achieve as a beginner. Whether other people think you have good taste is irrelevant to the quote/advice.
The point is to not let this discourage you from putting in the work.
That's not how I read the quote. I read it as him saying, you can't know whether or not you have good taste without first producing a lot of bad work, and that producing bad work is not necessarily a sign that you have bad taste.
If anything, those who judge themselves harshly are demonstrating good taste because they can see the flaws in their work compared to the works of others. It's those that don't feel any sense of criticism toward their own work that lack good taste, but they wouldn't feel this quote applies to them in the first place, because they wouldn't feel that their work is disappointing. They would instead be blaming others for not recognizing their superior work.
I didn't learn to use a command line or write python scripts instantly. I spent thousands of hours banging my head against the wall. Progress is slow. Imperceptible even. Stick with it and eventually you get there.
Does this mean everyone can do everything? No. It means you'll never find what you are good at it if you just give up at the first sign of failure.