I didn't particularly like this explanation

Honestly I've always hated this. An early example of the awful trend where there has to be a "lore reason" for every little detail.

Star Trek aliens are mostly humanoids because its a human TV show telling stories that have to be relatable to humans and also has a limited budget. There is no need for a lore explanation.

At least in this case it's a one off that's never really referenced again.

I agree with you in premise, there is a general trend to over lore in modern sci-fi. Things can't just be, they need some specific explanation.
This though, I didn't hate. It's always bothered me that aliens in sci-fi are just humans with shit on their face, their cultures are just aspects of our culture turned to the extreme, and every species' technology is around the same level.
Having a progenitor species that seeded the galaxy and that's why every intelligent species is basically the same is fine, basic but you know at least it makes sense and doesn't need to come up again.
Why are they the same, because a wizard did it essentially.
If they were true to how the universe works then every species they encountered would be crabs.

Eww, Q stuck his hand in Progenitor splooge!

i thought this was cool as a kid!

It’s a fun, well executed episode. It just happens to be one of those occasions where the Trek writers betray their complete misunderstanding of evolution.
- oh yeah, maybe so. i think for me, as a kid, it was a tale that showed me we, ie humans, are more similar and have more in common than may appear to us at first glance. good lesson at that time.
- Not to mention the scale of space and time

Especially since the solids share very little with the founders /s

Didn’t the founder lady say they were originally like the solids? Or am i misremembering?
- They evolved from solid life forms, but it was never established what kind of life forms. Could be humanoid, could be a bacterium. It would make no scientific sense for something as complex as a humanoid to evolve into something so different. But it's Star Trek, so anything is possible.

I want a hard reboot where there are no humanoid aliens at all.

No Vulcans or Klingons; hell, no bipeds at all!

Oops! All Tribbles!
- The Horta has entered the chat...
I remember reading about something that described this thought in a Star Wars fan site once. The stories that show human characters or human like characters everywhere, aren't really human at all ... they are more like place holders for exotic space alien beings that we can't even imagine.
I'd like to think that of Star Trek as well. The stories are just stories being shown for our convenience because the aliens they would encounter would be so strange and foreign to us that we wouldn't be able to believe it, let alone understand it
Then it wouldn't be Star Trek, which is primarily a sci fi representation of human social conflicts with forehead stuff as a stand in for racial differences.
- To the point that Nimoy set out to do “the wall coming down in space” for ST6 as the whole plot.
- I'm perfectly happy with it not being 'Star Trek.'
  I want a show where we encounter and deal with truly strange new worlds.
Babylon5 was much closer to that that Star Trek was.
- Well, the few advanced ones were. But all the others that needed to fit in the budget were all humanoid.

Salome Jens played both the alien that seeded the universe and the female shapeshifter from DS9.

And the Sphere Builder from Enterprise.

"There is something of us in each of you, and so, something of you in each other."

ghost side-eyeing Dr. Crusher

But first the motherfucking dinosaurs.

The founders would way anything to make the solids go away 🤷‍♂️

I haven't seen discovery so no spoilers

But it would be great if there was a bigger explanation that the general humanoid aliens were all seeded by the preservers while other more exotic spacefaring species evolved on their own hence the significant differences

Hard to say why specifically without spoilers, but I think you should at least try watching Discovery. It has some interesting ideas and is not altogether bad. I still like it the least out of all the series though. My issues with it are purely structural in nature (in short, too many things are rushed IMO).
- I slogged through the first couple seasons but gave up when they were the only ones who miraculously solve the Burn