I went to get my first road jersey today. I found one I liked and the overall fit and feel seemed right, but I was surprised at how short the front is. I am aware that it is designed for being used while riding where this makes sense, however I don't want to walk around showing my stomach if I adopt an upright posture. Do I just need to try a different brand or is it supposed to be like this? I'm a pretty average build and proportions.
Usually road jerseys will have different fits, both within a brand and across brands depending on the intended application.
If you have one with a short front it will likely be a tight fit intended for a racing position (i.e., low bar height) and typically combined with bib shorts which come up just under your belly button. Combined you will should not be showing your stomach even when standing.
That all said, if you are intending on riding in a more upright position, this type of jersey probably won’t be a good match as I find they can also pull across the chest in a more upright posture. These jerseys also tend to have a very tight fit, for aerodynamics, which can also be less than ideal for any off-bike situations. (For racers there is no such thing as an off the bike situation, even when sleeping).
I would personally look for road jerseys with a “casual” or “relaxed” or “classic” cuts. They will be a bit longer in the front and the shoulders will have more room for riding upright. Mountain bike jerseys (cross-country) can also work well in this application.
I'm tall (1.95m or 6'4) and normally take a large (XL in some brands). I've found Italian brands to come up short even if I buy a size bigger, but in most jerseys it's not a problem for standing/walking around, with non-bib bike shorts.
Of course if you get off the bike and stretch, that will make it ride up, and most jerseys won't ride back down again, unlike normal tops (this is particularly noticeable if you occasionally ride to the gym in a bike jersey and do chin-ups, combined with gym shorts that sit lower). After you pull it back down, it should be fine.
So you probably just tried a brand that comes up short, unless you're unusually tall and skinny.