Field guns can work for skeet, but they aren't optimal.
My Browning Citori is out getting its wood refinished, but leagues started up this week, so it was either use a field gun (Remington 105 CTi II) or defensive guns (870 Tactical, Saiga 12). Of those three, the 105 CTi is by far and away the best choice, but it's still no skeet gun.
Still, I shoot it well, and the first round I shot (first time on the field in months) was 24/25... way better than I expected. Problem is, I got too proud of myself and only shot a 20 the next game.
Keep in mind, though, the field guns tend to be designed around heavier loads (my 105 CTi wants to be fed 1 1/8 oz. at 1300fps, minimum), and those will wear on the shooter pretty quickly. The stock also tends to have a comb that drops off towards the heel, so it's a little more difficult to get a consistent cheek weld. Field guns like that Mossberg might work ok to get a shooter into the sport, it won't take long for him or her to start wanting something a little more suitable for the task at hand. If that's all you have, then great, shoot it and have fun. But if you're buying a gun for the game, you won't do yourself any favors by buying a field gun.