Therin of Andor wrote:
If you don't want your aliens to be alien, then don't use aliens in the first place.
Half humans, or aliens that look and act quite human, give human audiences something to relate to. This also applies to shows like "Superman", "V", "Battlestar Galactica", "3rd Rock from the Sun", "Mork & Mindy", etc.
I think you have to draw a distinction where part of the story is actually about the alien who looks human but isn't (possibly as a disguise) from stories about aliens generally. This is why I give Spock a pass - at the time, aliens pretty much looked and acted human so Spock was a revelation.
It must be hard to keep character origins fresh when writing so many episodes (another reason why I would have preferred them to focus on a more limited number of races in more detail) and hybrids allowed them to explore allegories about racism. I always thought Saavik's mixed heritage was a potential gold mine that they wasted completely as it could have given us a window into the psyche of a Romulan from an abused childhood struggling to attain emotional equilibrium.
I think they've had their day now though - there are more imaginative ways to tell the same stories in my view and I'm far more fascinated in exploring humans' interactions with other cultures. The notion that the audience can only relate to an alien if they look human or are part human could well speak to a degree of subconscious xenophobia on the part of the writers. I don't think we need to pander to that in the 21st century.
EDIT: Hey I just thought - I'm doodling an alternate universe TMP comic using screencaps and Gimp. I'll probably throw in some supporting characters from the 80s comics but with your permission I could bung Therin in as an Easter Egg. What is his rank, division, uniform colour, and post on the ship? If I get too ambitious, I might just have to cut and paste caps of Jeffrey Coombes from Enterprise.