The best part of Dark Shadows was always the relationships between the characters.
But a completely non-human entity would have been hard to accept.
Absolutely. Every "monster" on DS (for the most part) had a humanity to them. They suffered from human emotional frailties and the interaction between these characters and the "normal" characters was always wonderful. DS still has a good following today because the characters and their relationships are the heart of the series. These character-driven stories have sustained Dark Shadows' longevity, and have kept people interested in the show for decades. The supernatural element makes the show extremely unique, but the underlying character development and interplay is what makes the show a classic.
On the subject of random monsters, I absolutely agree with your comment about completely non-human entities. I can't see a place for a Creature from the Black Lagoon-type on DS. No way, IMO. Nor could I ever envision things like giant ants, tarantulas, killer robots, etc. ad infinitum on Dark Shadows. There is an enormous divide between the tortured, cursed beings of gothic horror/romance and B-movie monsters. They are two different things entirely. Or at best, in some cases, the latter is a MUCH watered-down version of the former.
Regarding sci-fi (and some other genres like Fantasy). Imgaine if you will....
Lara Parker's Voiceover: On this strange night, an otherworldly alien spaceship has landed before the ancient Old House on the great estate...
The door to the Old House creaks open... we see small, silver-clad, alien beings enter the house. They clutch mysterious ray-guns in their small hands as their almond-shaped eyes peer at Barnabas' portrait above the
mantle.
Suddenly, Josette's spirit appears to the aliens. The head alien shouts, "ACK! AAAK! AKAAAK!!" Then all the aliens fire blue and red beams of light from their rayguns. The rays go right through Josette's ghost, who shakes her head and silently weeps.... Just as I am weeping at the very thought of such a ridiculous scenario!
Ok that was dumb, but it was fun writing it. Anyway, yeah, that would have sucked.
~Penny Dreadful~