I’d say that’s all not very true, especially about the Ferengi characters. Quark is closest to the above but he actually understands humans and the Federation very well, better as time goes on, and that’s not surprising - he’s an adaptable and intelligent businessman whose job is dealing with dozens of other cultures. There are plenty of episodes where Quark is 100% Ferengi and 100% magnificent (The House of Quark is an obvious example). Some of this was at the insistence of Armin Shimerman, who was ashamed of the way he’d portrayed Ferengi characters in the past and was determined that Quark would not be comic relief.
Quark’s main hangup is that he has an unreasonable and sentimental affection for traditional Ferengi culture (which is actually very reminiscent of how first generation immigrants can be, being more traditional than those who never emigrated) which occasionally makes him act like an idiot. His brother and nephew, having less attachment to those ideas, learn from their environment and friends to become better people and better Ferengi - Rom ends up as Grand Nagus and Nog becomes the first Ferengi in Starfleet, but still every inch a Ferengi. Some other Ferengi characters (say hello, Brunt) are @$$holes but it’s not because they’re Ferengi, but because they’re @$$holes.
The same is roughly true of both the Cardassians and Klingons portrayed in DS9. Garak is many things, including a recent immigrant who learns from the other cultures around him, and he too understands other cultures (including the Federation) very well indeed. He changes a great deal, enough to become a leader of his nation. Dukat, similarly, understands other cultures just fine but he’s a fascist monster through and through, the hero of his own saga; he’s evil because of who he is, not because he’s Cardassian. Worf finally gets to show how he belongs in two worlds but has to choose neither and is, in fact, a better Klingon than most (and is recognised as such) as well as recognising that it must be Klingons who change the empire by no longer tolerating its hypocrisy.
And thus we come to the final invasive culture, the Federation. DS9’s Federation characters are immigrants and visitors too, and they know it, and they too learn and change as a result of engaging with those around them. They’re certainly not the most reasonable people about - they make plenty of mistakes about people, and Sisko is famously far from perfectly reasonable; but he is a good leader who’s aware of his responsibilities, and generally discharges them effectively.
As an immigrant who’s lived in four countries (South Korea, the U.K., New Zealand, and Canada) and whose cultural identity is kind of all over the place (mostly English but also quite Korean) I appreciate the sensitive and nuanced approach DS9 takes towards multiculturalism and the immigrant experience, and honestly I’m not sure it could be made that way now - by Americans, at least.