I think the disagreement in this thread comes from different posters' riding habits.

If a person is riding more than trivial distances, then the most comfortable solution is a high-quality pair of Lycra shorts (or bib shorts) with a good chamois. In fact, I can't even recall the last time I saw anyone (on a group ride, event ride, or race) wearing anything else.

If a person is doing token rides on their vintage bike or just toodling around town, I suppose gym shorts or cutoffs are okay, or even a liner under cargo shorts. But there's a reason why people who actually ride a lot almost universally wear good Lycra shorts with chamois.

A person surely can ride long distances with gym shorts -- I did that on my first century ride when I was in HS. Of course, I was pretty ignorant, and didn't have much money, and didn't realize that I was a lot less comfortable than I could've been.