The original Star Trek and Captain Kirk as a character were much closer to portraying a "Navy in space" than the socialist ideals that would start to creep into TNG.

Although I find your criticism to be fair for TNG itself - when Roddenberry had greater creative control and the Federation began to be developer as having evolved beyond petty human desire and conflict, although there were some exceptions because sometimes the writers didn't get the memo (Barclay's OCD tendencies and Geordi keeping a holographic girlfriend come to mind) and it's just impossible to write good drama where all of the characters are just insufferably perfect. Even Superman has to have kryptonite.

But TOS is the series where McCoy is pretty openly racist towards Spock and where people get into fistfights all the time - it's a lot more grounded in plausible reality.