Yet people can and do break in. Your internship on a weekly newspaper is a good example, especially if you can show bylines or other evidence of your work. Another example is having a portfolio from other sources, such as working on the publications of a nonprofit organization. Or your parallel experience might be in an allied field, such as public relations, or in a particular lane of journalism. You probably know that more journalists work for specialty or industry publications than at newspapers.
Professionalism comes in a variety of ways.
You might be surprised at how casual certain job-seekers can be, beyond looking the part at an interview or sending resumes around in a mass mailing. Persistence is probably the area with the biggest payoff. Covering the traditional bases is relatively easy. Adding a dimension of creativity to the search, such as finding a different set of contacts at your target organizations, is where the challenge lies. Write to people whose work you admire.