Certainly not.

For one thing, most ancient armies were citizen levies, not professional forces. The people who fought were ordinary people whose physique was determined by their everyday life. While many of them would have been reasonably fit from hard work on their farms or elsewhere, being in shape for war would require long-term dedicated training on top of that everyday workload, and understandably few people could be bothered. The ideal in many societies was that the leisure class, who did not have to work for a living, should spend its time training and form a warrior elite - but of course the life of a rich person is filled with pleasures and distractions. Several Ancient Greek sources depict rich members of the militia as pale, fat and out of shape rather than lean and toned.

(Obviously the fully professional Roman army of the Imperial period is probably an exception here, but one on which I'm not qualified to speak.)

For another, the body we see in modern movies can only be maintained with a very particular diet and training regime. This would be actively harmful to an ancient soldier, whose existence was one of hardship and deprivation. The ideal warrior was one who could go without food, drink or sleep if necessary. This was not compatible with the lifestyle of someone who was trying to get or stay jacked. The Greeks themselves regularly commented on the fact that professional athletes, with their habit of excessive eating and sleeping, did not make very good warriors.

You can read more about all this in my older posts about Spartan training and the bodies of Spartan men.

When you see the ideal male body in modern pop culture you have to bear in mind that this is because it is our ideal, not because it reflects real history. Ancient Greek women also pursued a very different beauty ideal than the wasp-waisted actors with free-flowing hair and off-the-shoulder dresses you see in movies depicting them. Simply put, we like to see beautiful people in the media we consume, so we put in people we think are beautiful. You could consider asking where the modern male beauty ideal of the lean, jacked, waxed fragrance model comes from.

To describe the body builder or jacked action movie star physique as "unrealistic" is a colossal understatement. Firstly, it is an unsustainable physique. It is something that is only attainable temporarily for a brief window of time, it is not something that can be maintained 24/7 over long periods. This is especially true for the body builder "Mr. Universe" look. These require going on crash diets which bring out the definition of muscles and veins.

It's also worth noting that these looks are purely aesthetic, and they are extremely unhealthy. The pre-show crash diets that body builders do typically put them close to dehydration while also reducing glycogen in muscles (this is what gives them that lean, sculpted look). However, this gives an appearance that is completely opposite of reality. The reality is that someone in this condition has much less endurance and is more likely to get injured. A similar story exists for folks who just have very low body fat percentages in general, in the low single digit percentages for those "jacked" movie star physiques (like the "Spartans" in the movie 300). Having a low body fat percentage is difficult to maintain and puts one at risk of all sorts of health problems (including heart problems, immune system weakness, lower bone density, etc, etc.) And for women it can even stop the menstrual cycle.

The bodies of actual warriors typically have reasonable levels of body fat, and they tend to look more like the bodies of competitors in strongman competitions or like construction workers than like jacked movie stars. Stocky, filled out, plenty of muscles, but also plenty of curves, and sometimes even a gut. This is the difference between the teenage fantasy of a warrior physique and an actual warrior physique. Typically a warrior would only end up with a highly sculpted look by accident, due to malnutrition or dehydration, which would be a detriment to anyone who actually needed strength and stamina on the battlefield.