If they hired you and determined in 2 weeks you were a bad fit that proves they are shitty at selecting employees.

If I were you I would do a couple of things before I beat myself up - if you experience this kind of thing at your next job then perhaps I'd worry, but 2 weeks at one company? (1) - Do a little research on the company (glassdoor tends to be negative but still worth looking into, google the company and see what other people's experience has been). (2) - Do some freelance work and see what the feedback is from who you do work for.

What feedback did you get in the 2 weeks you were there?