When TNG wanted to actually portray their aliens with diversity and depth, they did it pretty well.
"The Wounded" gave us a pretty 3-D intro to the Cardassians, and "Ensign Ro" to the Bajorans.
With the Ferengi, odds are that since they had decided the Ferengi were going to be comic relief there wasn't much point. Except for Daimon Bok and that Ferengi scientist Dr Crusher was friends with.
The Klingons did have the whole "Space Mongol" look, but aside from that they were written to have no real distinctive traits besides being antagonists to the Federation. You could have just had them be renegade humans and there'd be no difference.
Which is the crux point: TOS had them be visually different but otherwise wrote them with no race distinctions in mind, where TNG usually associated characteristics to their aliens to go along with the appearance.
As for Spock and McCoy, Spock was just as racist as McCoy was which also made him a hypocrite: He'd go on about all of humanity's flaws, but always conveniently forgot that the Vulcans used to be worse than humanity EVER was.
"The Wounded" gave us a pretty 3-D intro to the Cardassians, and "Ensign Ro" to the Bajorans.
With the Ferengi, odds are that since they had decided the Ferengi were going to be comic relief there wasn't much point. Except for Daimon Bok and that Ferengi scientist Dr Crusher was friends with.
The Klingons did have the whole "Space Mongol" look, but aside from that they were written to have no real distinctive traits besides being antagonists to the Federation. You could have just had them be renegade humans and there'd be no difference.
Which is the crux point: TOS had them be visually different but otherwise wrote them with no race distinctions in mind, where TNG usually associated characteristics to their aliens to go along with the appearance.
As for Spock and McCoy, Spock was just as racist as McCoy was which also made him a hypocrite: He'd go on about all of humanity's flaws, but always conveniently forgot that the Vulcans used to be worse than humanity EVER was.