I think the problem is, ultimately, that science fiction grounded fully in known, accepted science, and not violating anything and only allowing what is reasonably possible is so restrictive for any exciting fiction for the masses.
Stross and Egan are perhaps two that really are capable here, but unfortunately, the concepts presented require some level of complexity. Otherwise, the only options are then to:
a) "Magically" circumvent the inihibting factor (warp drives, teleporters, light sabres etc.) due to advanced technology based on misinterpretations due to bad popular science - EvE Online videogame suggests that the multiplayer 'lag' due to numerous connections is a result of Lorenz time Dilation. It also claims that superluminal communication is possible due to quantum entanglement.
b) The same as the above, but the technology is from a different source that is not bound by our human issues with laws of physics. i.e. the TARDIS of Doctor Who, the Navigators of Dune etc.
Personally, I am not too bothered about such magic when it's purpose is part of the setting, not part of the plotline. By which I mean that it is established and can be taken as given , something I can put in my 'suåpension of disbelief' box from the start - and it is not later relied on or forms a Deus ExMachina escape route. he magic must be self-consistent too.
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The idea that Star Wars is Science Fantasy and Star Trek is Science Fiction is a common misconception.
Science Fiction is typically described as that whereby a principle is extrapolated to an extreme and the effects or results on society or humanity explored.
Star Was has no scientific postulation whatsoever, it is pure fantasy. It's set in space or on other planets, yes, with technologies like laser guns and such all of which is irrelevant. The story is a clich€ fairy tale. Antihero comes across cryptic message in a bottle, seeks help from wise old wizard who then gives him magic sword and teaches him some magic. They rescue a princess with the less altruistic, but ultimately on-the side of good swashbuckler - the wizrd is defeated by the Dark Knight who, it transpires, is the father of the princess and the antihero (whom the wizard raised in secrecy) blah blah blah. It even begins "Once upon a time, in a kingdom far, far away" just slightly reworded as a "galaxy".
Star Trek was a little more in the science fiction vein, but purists may still disagree. It was an idealistic social commentary that required a far future because otherwise it would have been rubbished and potentially even considered offensive to some extreme rightwingers). The precept here was simply parables but with the variety of different planets or alien cultures to provide the versatility in telling again, clich€d story motifs.
Of course all TV shows and movies ultimately are, despite how much care and creative process goes in, still products of their individual eras. Depsite Star Trek's multicultural and humanitarian ideology, Yeoman Rand must still provide the Captain with COffee and all female unifromrs entailed ridiculously short skirts, whilst the men watched from their elevated authoritative positions. The inconsistent Star Fleet only seemed to be concerned with Kirk's irresponsibility on occasion, and the threat he posed to his crew was always brushed aside because he ultimately saved them all from the danger he largely participated in creating. Helped by the wise, pointy-eared elf, now no longer a subhuman outcast creature from folklore, but an alien being with 'human rights' and much wisdom through their purely logical expressionism, Spock personified the antithesis to Doctor McCoy, the superstitious and conservative shoulder angel.
