BAD Writing . - IMO voyager was plagued with bad Writing, they had great ideas, but often by the end of the episode it was the easy way out. Like when Janeway decided to go trough Borg space, I'm sorry but no one sane would do that, but she read the script and knew Kes would help them out. ......... because if Kes didn't have her 'evolution' they'd all be assimilated and dead. ... well that's my personal ending to voyager. - It's like when Tom Paris 'becomes' a rebel out of no where, and it's supposed to be believable, and he's just faking it for a secret mission. They should have done that episode way earlier like when the Maquis where still having difficulty adapting. I don't think anyone would have bought it in reality, not even the audience. - All this to say, and emphasize. Bad Writing.
VOY was plagued with good ideas and poor execution. For a ship alone in the unknown, they don't seem to have problems with supplies or morale, and even after getting into phaser fights almost ever week they have surprising little battle damage to patch up. Their crossing the DQ should have been much more of a struggle. Another thing they could've done differently, which would've made more sense and brought a lot more tension to the ship/crew would have been the Seska storyline. I never got why since she was revealed as a Cardassian she had to leave the ship (why? What could she possibly gain from staying behind with the Kazon?), it would have been much better for her to stay onboard, as a source of tension for the rest of the crew. Meanwhile, before the episode where she was uncovered Jonas should've been introduced, and been working in the shadows with the Kazon, and then frame Seska for it. They could have done so much more with Seska remaining on Voyager it would have been great fun to have watched--even if they did decide to kill her off later.
The gravity alone doesn't cut it. Wouldn't they look very differently if their heavy gravity genes started growing on lighter gravity worlds? If Vulcans looked normal for their species and Romulus had Earth-like gravity, wouldn't Romulans all be like 18 feet tall and look like they were suffering severe muscle atrophy?