Don't mean to make this all serious but sure you could talk about how god or a designer was just playing around or you could think about how the environment and the selective pressures were different during this period of the planet's history.
This befote the META became all about efficientely killing everything while wearing armor. This the ptelapsarian world before the spinal catastrophe.
After that point, you can't just "be yourself", you'll just get ganked. So everyone started putting all their point in attack and defense, variety massively got reduced and everyone became a servitor of Moloch while existing only so that the mindless universe could suffer the pain of its own entropy.
I'm sure that there are planets all over the galaxy where the same or similar creatures evolved and didn't get wiped out but instead evolved into higher animals.
Our lineage was lucky to go on to create humans because all the other ones got wiped out in the Cambrian for some reason.
If those same creatures had survived, they would have evolved into more unique forms of life and we would have called them aliens.
Funny part is, those same creatures I suggested that might exist in alien worlds might one day run into us and look at us like some kind of weird animal that might have evolved out their own planet's Cambrian extinction event.
The biggest fiction (constrained by budget obviously) of shows like Star Trek is that most of the intelligent creatures we might possibly meet will look almost exactly like us. I don't think even the people coming up with Star Wars aliens have the imagination to get it right. They still base it on what we are limited to thinking up as humans and our own likely narrow understanding of what is life and what is intelligence.
The second-biggest fiction is that it would be possible for us to coexist on one planet's surface considering our needs when it came to gravity, atmospheric pressure and basic atmospheric composition would be very unlikely to be the same.
But that would narrow the scope of a lot of sci-fi, so I let it go.
I always felt that humanoid aliens were also a way to get the audience to more easily emotionally connect and treat them as characters. Its hard to portray a truly alien lifeforms with alien behavior like you would find in a speculative evolution fiction art book while also giving them a human understandable emotionally driven narrative and space age tech for the plot of a story. Its easier to relate to blue cat person than to the Blob I guess is my point.
I really like the comic Humanity Lost for its better representation of alien life in its story. The author really cares about that kind of world building ad im here for it really great stuff.
"They reproduce by doing what? Why? How? Wait almost a whole solar cycle? Give birth? Then they can't take care of themselves? ... How did these beings even survive this long to evolve?"
tbf there are some pretty weird looking creatures in the ocean even now. Like, would the giant deep sea Isopods really look that out of place next to stuff like Anomalocaris? We still have plenty of spiky worm shaped things living on the bottom of the ocean. And for the softer side of animals, would things like siphonophores really look that out of place in a lineup of Cambrian fauna, if placed there and shown to someone who wouldnt have the knowledge to recognize what they actually were?
Cambrian seems like heavens design team didnt have an established meta and were just having fun with it. Once the horse design got approved the engineering team got lazy and used it as the base for everything.
Chordata is the third-largest phylum of the animal kingdom (behind only the protostomal phyla Arthropoda and Mollusca) and is also one of the most ancient taxons.
These are all immensely powerful evolutions. We got the Knifey Tortoiseshell, Cheval De Frisetipede, Sucky Long Mouth Humpback Trilobite and Sabertooth Flatworm. All the greats!