Well yeah, and that's why the current Forgotten Beast/Titan generation mechanic is not the end goal. Toady intentionally started off small to test the waters a bit. He knows it's a limited mechanic and doesn't pretend that it's not.
I didn't say you can't make a better random-creature-generator, I'm saying that there's not the same sense of attachment if you ended up with a random new specie to learn every time you make a new fortress. Dwarves love stone and booze and magma and complicated machines, and I can work with that. I boot up a new game, and I end up instead with lizard people who live in a swamp, take pride in working together to hunt for food, because at three feet tall, even regular wildlife is a serious and noble effort to take down. They don't revere nature, but are good at using it, having several beasts of burden for every job, which of course double as food sources and makeshift guard animals. Their magic tends to make use of plants and fungi, and while they're not generally considered hostile, due to their stature and preferred living areas, don't tend to trade with outsiders out of a simple lack of shared desired goods. Of course, I also get a long list of materials they prefer to work with and items they tend to make, their preferred food, how all their dozens of unique farm animals work, the history of their culture, what a major city is like verus a minor hamlet, how they structure themselves socially, what religion they practice... I'm just glossing over this all, but look at the size of this paragraph already! I'd have to study these guys for hours before I even know if I'm
supposed to strike the earth! Maybe instead, they make long reed-mat walls, and patrol, using their large numbers and excellent swamp-movement to their advantage. They prefer using spears and traps due to their small size and weak stature, but since they live in soggy environments, avoid armor for the most part. They don't use bows because items made of wood and rope don't last in excellent condition for long, instead preferring slings, which in their more established militaries, use magically imbued rocks. Lacking in formal education or the ability to engineer large structures, they are surprisingly well informed and knowledgeable, due to their ability to quickly grasp what everyone in a large group is saying, so while most races would find a large room full of talking people to be just meaningless noise unless you can tune everyone out but one, these small lizards can learn about fifty points of view at the same time. Although they evolved for swimming, they have learned to use their claws and agility to expertly climb trees, although on a whole they tend to dislike heights. Because of their light weight and lack of armor, attacking groups often find themselves ambushed from above, and because of this learned ability, they carefully tend large trees to grow in their swamps, where they would normally have trouble growing. Although they tend to use traditional items and techniques, it's not because they're trapped in their past, but because few items stand their corrosive environment well, but the few new technologies they can use tend to be adopted almost instantly. And, well, who read all that, let alone the next ten pages I'd need for you to properly understand these guys?