Remember, a mass-extinction event and massive climate change were the only thing that wiped out the Dinosaur's competitors, the Crurotarsans and allowed them to dominate the planet for a long time.
Inhuman is not non-humanoid, for various definitions.
Bipedal? I think a good case would be made for having limbs free to use tools is probable.
On Earth, at least, bilateral symmetry is mostly true. So, two arms (a left and a right) and two legs. Same for two front-facing eyes (for depth perception; especially needful for easy, successful tool-use). Almost all Terrestrial creatures put air-intake and food-intake near the sense organs (probably necessary to see what you're eating, pick out the bones/avoid the thorns). So, you've got a face. Likely, since most things are vertebrates on Earth for a long-time, that the head is above the other limbs. Reproductive organs are near excretion organs for most species, and not near the head, so that goes towards the tail.
Tool use is going to almost require a thumb, and manipulative digits, which is going to give you a hand. You might get away with tentacles/lips, like the Puppeteers. But you'll need something with which to make your tools.
These, IMHO, mostly make a humanoid.
Given that the Earth has had many mass-extinction events - including the one we're living in right now - I don't see why it's far-fetched to believe that mass-extinction events happen on other planets. If it happens once every hundred million years... it happens more often than it has here on Earth. Given deep time, you can do all the things.
Please define 'mammal'. Warm-blooded (which is out of favor scientifically, I've heard) allows animals to handle bigger changes in climate - versus cold-blooded, which allows more animals per-square-foot (costs less energy). Any time you start having climate change events, or varying climates - you're going to select for warm-blooded-ness. As well as fur/hair or feathers; for their insulation properties. So, something sorta like a mammal will probably exist, if your planet has wide-enough climate swings. You may or may not get boobies. You'll probably get live-birth (either egg-eggs stored internally, or eggs without shells/yolks/raw fetuses). You may get immature live-birth (marsupial). r-selection will probably be ill-favored, especially if you're dumping a lot of energy into having brains for your species.
Sapience is a good question. Of course, any space-faring race is going to have achieved it, ipso facto. And those are the ones we would be interacting with. Those that didn't develop it, will just be interesting animals. Chimps are interesting animals. There are probably a lot of interesting animals in the universe. Uplift might be a solution to that.
Fossil fuels rely on lots of plant growth without attendant decay, and being geologically buried... or, perhaps hydrocarbons squeezed from the primordial matter of the planet. That all happened before we got termites and other saprophytes evolved to recycle our carbon better.
Do I think Star Trek is right? F no. We should have crabs, spiders, aquatic insects, octopii, trilateral symmetrical, and a wide variety of other types of aliens. But, we would also have humanoids. Some that might even look kinda close to human.