A flip side of the question, "How "realistic" should STAR TREK be?", could anyone envision a Trek series that is a cross between Horatio Hornblower and "Gulliver's Travel's" meets "Dune", with a side of "Star Wars"? If such a series took place, let's say, 3000 years into the future (instead of 300 years into the future), I think the series could work. The level of science and technology would border on looking like magic to us, and the culture would be nearly unrecognizable, with nearly ZERO reference to Earth. That is, assuming Earth still exists as "Earth". For all we'd know, Earth in the future would be a barren wasteland, or one big park reserve and heritage site. Couplings between humans and anything imaginable would be the norm. Changing one's appearance, including sexual characteristics would be like changing clothes. And maybe, augmentation for maximum adaptation on any given world would justify the "humans with bumpy-foreheads" trope. Then again, what makes STAR TREK special is that while the franchise pushes the sci-fy envelope, it still has elements that is recognizable for today's audience. It certainly did when I first watched TOS, back in the day...
Kirk met Apollo. Not the fella from Galactia, the Greek god himself. And he beat him. In the animated series they met Lucifer himself and he wasn't that bad of a guy, they all travelled to a dimension of magic and shot rainbow beams at each other. I like Star Trek where anything goes. But still, they need that recognisable and relatable core group on the USS Enterprise to experience this bizarre stuff. They're our surrogates. Make them unrelatable and the show ends up a sequence of events with no emotional connection.
I love the more fantastical stuff. And would certainly be intrigued by the kinda show you described, whether it was labeled "Star Trek" or not.
The Red Angel stuff is what has me interested in Discovery this season. I've always been a fan of the fantastical elements, though they can keep the Q civil war stuff.
The fantastical, over-the-top stuff is part of what made TOS stand out. Bring on the gigantic amoebae, space gods, and anomalous humans who live for thousands of years! Kor