Expecting realism of any kind from what is essentially an artificial fantasy construct is in itself kind of absurd.
You're confusing Realism -- which is the idea that characters in a story should display personalities that seem like plausible representations of real human personalities -- with Naturalism, which is the practice of creating convincing re-creations of physical environments and of the physical world.
Not at all. First of all, 'plausible representations of real human personalities' does not need to include every possible thing a real world person would do, say or think. We need not see the characters eat 3 meals a day or sleep or burp or excrete or read or vomit or scratch or yawn to assume that they do in fact do these things.
Secondly, and more to the point, these characters are as much a construct as anything else in a fictional world. Applying the test of 'real human personalities' to them is useful, but only to a point. A point which is determined by the type of story, it's purpose for existing, the target audience, the resolution/fidelity of the character etc. One of them isn't even human, so in his case requiring 'real human personalities' is getting off on the wrong foot entirely. As for the companions, these expectations are fine, but only within the parameters dictated by the creators of the fictional world.
In the past the creators of the show saw fit to exclude any notion of romance between the doctor and a companion. Not only do I respect that, I think that it works very, very well, for reasons I have stated elsewhere.
I am not adverse to romance or sexuality depicted in other shows. There are shows that are 'right' for that kind of thing, and those that aren't. Those who have long enough memories may recall that I was one of the people who campaigned rigoriously for more overt sexuality and titillation in
Enterprise during it's run.
Nevertheless, depictions of romance between the doctor and a (human) companion are just not something I want to see in
Doctor Who. I find the thought particularly vomit-inducing on the whole.
It has nothing to do with the doctor being limited to an 'incomplete character' because of it. Romance can be explored between the doctor and others beside the companions, if you really need to see that kind of thing. I quite enjoyed the first doctor's flirtation with Carmeca in
The Aztecs or Madame Pompadour in
The Girl in the Fire Place. But the companion is placed in a situation of trust with a being, a different species entirely, of vast intellect and age and experience. Sure one who could, if he wanted to, sweep her/him off their feet, but I feel that would be an enourmous betrayal of that trust, a misuse of his position of power and a step backwards for the character. It essentially undermines the character as I see it.
And speaking of exploring characters, well this can be done in different ways apart from putting them in a romantic situation. One of the interesting things about TOS is the friendship between the lead characters. The 'bromance' if you will - though this description hardly does it justice and only serves to denigrate it imo. I don't need to see Kirk & Spock in bed with each other (though there are plenty of slashfic people who relish the thought) - such a notion makes me feel slightly sick tbh. But the friendship that exists there is something that is very inspiring imo, and the depth that it gives to both characters is above and beyond what is often seen in typical onscreen romances. Forcing the view that it's actually a romance rather than a friendship only serves to sully and degredate what was/is a noble depiction of friendship.
I know that many fans will never let this go and will keep pushing for Doctor/companion romances to be the focus of the show. That's fine, but just accept that many classic fans like myself really don't want the series to go there, and it's not necessarily because we are close minded or shallow or prudes or that we want incomplete characters or anything like that - these are complete mischaracterisations and are, on the whole, incredibly shortsighted and wrong.
Cue 40,000 word response...