I think people overstate that difference. Yes, the designs of the aliens and landscapes are able to be more imaginative and exotic, but the concepts aren't really that much weirder. Megas-tu isn't intrinsically weirder than the "Catspaw" aliens. A giant Spock clone isn't intrinsically weirder than a giant Apollo. The Lactran zoo isn't intrinsically weirder than the Talosian menagerie. A shapeshifting Vendorian is no weirder than a shapeshifting salt vampire or Garth of Izar. Radiation shrinking people is no weirder than radiation hyper-accelerating people, or Flint shrinking the Enterprise to sit on his tabletop. An alien that can split into three parts isn't much weirder than a society ruled by three candy-colored disembodied brains.
The goal of TAS was not to make a kids' show or a silly cartoon. The goal was to make more Star Trek, as much like the original series as possible, but taking advantage of the medium's greater freedom to show imaginative vistas and aliens. The only concession to the children's time slot was toning down the sexiness and onscreen violence.
So it bothers me that these shorts supposedly "celebrating" TAS seem to be treating it as a joke.
And maybe the makers aren't celebrating it. I don't know; have the makers of these Very Shorts said anything about why they're made, or addressed the contentious result from fandom?
I'm in total agreement with you in how animation can lead to a truly more expansive universe with creative liberties that could otherwise not be done.
Also agreed; TAS was never meant to be a kids' cartoon, but a less expensive way to tell new stories and in a more expansive scope that the live action original could not do.
But mainstream/general/casual-viewing audiences think it is. They also seem to be the target demographic. The new Trek series generally have been aimed in that direction. This reminds me of some of the slinging I've seen in other forums, which include the use of the word "gatekeeper". If fans aren't, all I know is that the fans don't make the show, some who are fans who make the show can do a bad job of making it (regardless of how popular it is or is not), and the makers still have to get large enough audiences - which means more than just a handful of ardent fans are going to want to ultimately feel included as well. If more of them, including many others who never cared for TAS or hated it, or even those who like it think this type of parody works, that's the format they'll stick with. It's hard enough a juggling act to begin with...