And Gowron. Also the Cardassians were already set up in TNG, as well as the Ferengi.
As said before, don't confuse species with characters. The Klingons and Romulans were TOS holdovers, used by TNG, but no one has issue with that.
Maybe, but it's still something that would be better off with Romulans as the 2nd crew.
Agreed, but they probably didn't want to do make-up for a bunch of extras. Hence Voyager's ridiculously high proportion of humans.
No one on the writing staff believed they'd be trapped away from home forever, so they didn't care to write the characters that way either.
One of Voyager's longest running inconsistencies... at least some characters should have married, had kids, and basically acted like they were going to be out there awhile.
Too little, too late.
Well what do you want me to do about it? Travel back in time and start grabbing random viewers by the throat and shouting, "HOW DARE YOU NOT LIKE 'VOYAGER'?!"
Sure, they could do that...if the main cast was smaller so that they didn't feel like they were screwing the main cast out of spotlight.
DS9 found a pretty decent balance, and it was juggling 20 or 25 characters by the end.