Sure. It's even possible to be very familiar with violence and not be good at warfare; think about the difference between a warrior and a soldier (current US military propaganda notwithstanding): a warrior is an individual. A soldier, by definition, is one element of a fighting group. Being good at one doesn't automatically mean being any good at the other. You could imagine a species where singular dominance battles are common yet the idea of ganging up in an organized fashion beyond temporary and immediate groupings of convenience never took hold.
And it starts at the basics: modern military training and indoctrination is the result of decades and even centuries of hard-earned experience in what works and what doesn't, and it's always evolving and being refined to take into account cultural, societal, and technological changes. It's not something that can be avoided.
A good example is the American Revolution. Historical myths to the contrary, it wasn't a bunch of freedom-loving non-military farmers who took up arms and defeated the British Forces out of pure patriotism and the power of liberty; just about all the British military defeats relied on the colonists eventually fielding trained forces. Even Lexington and Concord. Historical research has shown that a great many of the colonists were in fact veterans of the French and Indian (or Seven Years) War, and thus trained troops; if anything it was the British at that fight who were inexperienced, many not having previously been in a conflict. But on a larger scale, the Americans spent much of the early part of the war in constant retreat until they'd accumulated a cadre of battle-experienced troops and imposed traditional European-style discipline and training so they could have a chance in open battle.
Which Washington, incidentally, was well aware of; an experienced soldier himself, he had a low opinion of amateur militias based on his own experience. The army that took to the field at Yorktown was a professional, conventional one. And the same lesson had to be learned in 1812. And 1861. At least by 1917 they figured out you couldn't throw untrained troops into the meatgrinder of modern warfare and expect them to survive with only the love of liberty protecting them. Turns out that isn't very bulletproof.
Not that this is a uniquely American thing; the Russian communists had to figure out the same lesson. It took Trotsky reorganizing (well, creating, essentially) the Red Army, employing experienced former Czarist officers and non-coms to train the troops, before it became really effective on the battlefield, having realized revolutionary zeal didn't overcome aimed firepower and professional military tactics.
You'll note in those two example technology wasn't the important factor. In both cases the two sides had at least equivalent weapons. Both sides had literate leadership capable of reading and knowing the theory of successful warfare based on history and the experience of others, but it took until they had troops drilling on the parade ground with sergeants bellowing at them, mattresses being tossed in the barracks for not having the corners done correctly, and people doing pushups until they puked until they got it into their heads why you only pointed the weapons downrange that they could get on the battlefield and be expected to win and not have to rely on luck or the enemy screwing up.
Relevant to your question, in both cases these are human groups, in real life who had to learn that lesson, and you still see it happening today. People who think that because they've got a military weapon they can take on a military force. Give me a bunch of yahoo "militiamen" and a company of Marines (US, Royal doesn't matter) or from just about any other professional military with the same weapons but half the size, and they'll cut through the "militia" like a hot knife through butter the vast majority of the time except in very specific circumstances. And again, these are people who have access to lots of history and documentation demonstrating over and over why some things work and some don't, and yet that information simply isn't incorporated, despite example after example why it has to be.
So that being the case with humans in reality, it's hard to argue that aliens in fiction couldn't have that same sort of problem. The difference being, in the case proposed, the aliens are smart enough to realize they have the problem.
ADDENDUM
There's another factor that could come into play. Humans seem to have an inherent hierarchical instinct where people will naturally form groups and will tend to follow those in a leadership position, however that leadership is recognized as legitimate, whether through the leader imposing their will and control, or whether the group chooses the leader, or anywhere in between. That makes organized conflict something also inherent and natural; note that the most popular sports tend to be team sports, and what are team sports but organized, controlled, conflict between groups operating in a unified, cooperative manner? It's such a part of us that even our recreational and play activities exhibit it.
Another intelligent species might not have that instinctive "feel" for that sort of behaviour. They might have evolved as more solitary creatures, and recognize intellectually the benefits of cooperation, enough that they've built a civilization, but don't have the instinct to cooperate and follow orders from a leader that humans have. That's going to have repercussions, especially if you combine that with sketchy knowledge of military training. In stressful situations, most people will look to someone to be in charge of the situation and will follow instructions, an instinct military indoctrination reinforces. In a species without that instinct, someone given orders might stop all the time and consider if that's the best thing for them to do, which in a battlefield can get you or other people killed.
