But I think Roddenberry was advised that intelligent life, it if evolved on other worlds, would/could conform to human development here ... kind of like parallel evolution. It's having the opposable thumb, I've heard, that was key for human's developing tools, etc.
That's what some scientists used to think, but it was typical ethnocentrism. SF writers, artists, and scientists over the decades have come up with a lot of plausible nonhumanoid designs for intelligent, tool-using life. Heck, there are examples of viable alternatives here on Earth. Therapod dinosaurs were bipeds with their forelimbs free, so they could've theoretically developed opposable thumbs, and been a tool-using bipedal race with a very different body plan from the human norm. Elephants' trunks have great dexterity -- imagine a similar creature with two trunks, each ending in multiple fingers. Or consider the intelligence and dexterity of the octopus or squid. Imagine a similar organism developing the ability to move on land -- or developing a civilization in the depths of the sea.
So the "convergent evolution" idea is really just an excuse for using humanoids in fiction if that's what your budget or storytelling preferences demand. It's not really sound science. Sure, there could be some
aliens out there who've developed a broadly similar body shape, but they wouldn't look like human actors in prosthetic makeup or be able to wear off-the-rack human clothing.