Well, if you look at TOS and film spinoffs, the ships were much closer in appearance. The Romulan Bird of Prey and the Klingon cruiser designs both had the same overarching design (with the warp nacelles kept at a distance from the hull). It's not 'til nearly a century later, in-universe, that you start to see designs like the Ferengi ships and the Defiant, but by then the technology would presumably have evolved to an extent that newer designs were possible (besides the fact that different civilizations would probably have found different ways to deal with warp field dynamics -- things often seem impossible 'til they're done).
That's what design creep looks like when there's no realistic constraint. It's like speculative architecture. Some of that stuff might be possible, but most of it is butt ugly. And a lot isn't even possible. But people are developing it because it is different
Anyway, the different solutions argument only works if physics are different from one place to another. Grossly speaking there are probably dozens of material configurations that will make a thing that is watertight and floats. But ocean going ships all have the same basic hull shape. Because physics.
If the Cardassian solution to warp physics is worse than the federation solution, they would have moved their designs toward the Fed shape. If it's better, Federation design would trend towards the cardassian shape. If it is equal, everyone else's ships would look fed like or cardassian like.
The possibility that warp physics has a dozen or more equally effective solutions, after roughly 800 years in this corner of the galaxy, and nigh on 2000in the Gamma quadrant, is thin. The problem boils down to design creep, pure and simple. I don't mind post hoc justification for fictional elements, but a post hoc justification doesn't change what my examples mean in the case of the Transformers.
Form may follow function, but one could make a point for alien technology that fulfills an analogous function could still have a different fundamental basis and thus look considerably different. For instance, if an alien culture developed organic based tech instead of mechanical based tech, or projectile weaponry that uses repulsive fields instead of controlled chemical reactions. Plus, there is no shortage of examples from human history of needlessly ornate weaponry and armor.
This still takes the form of a post hoc justification. The Movie Transformers we're not organic and seem to use kinetic and particle beam weapons.
Abrams are basically just kinetic weapons 2; electric boogaloo. Ultimately the forms of defense will follow the same logic I outlined before.
But let's say they have a force field technology that justifies the angles and pointy bits that would serve to help enemy weapons penetrate (just like the weird armor of our past, and why practical armor evolved away from ornate details. Also why people who understand the principles of things like plate and mail have such disdain for "boob armor." Boob shaped armor is a good way to help guide the enemy's sword through your sternum). Why can they punch through the force field? Anti-aircraft force field does not fit, because that would make throwing the enemy pointless. As we see the robots throw each other often enough, it's likely that we aren't dealing with a force field technology that does anything useful in hand to hand. Which makes one wonder how it can stop bullets, and why it's vulnerable to discarding sabot rounds? It's clearly not the dune style slow weapons pass thing because the whole point of a sabot is to make the bullet much fast.
My point is not that other solutions don't exist. It's that the artist who sits down and justifies the images then remains consistent with that basis is a rare thing. And the reason it is rare is that audiences don't easily grasp the logic. They do grasp blue eyes are good, red glowing eyes are evil. They understand that alien is equal to strange looking, so by making the robots pointy, and giving them lots of strange planes and angles, we can gloss over the fact that the have the same trunk plus five limb bilateral symmetric body plan as we do. And, in general, it works.