Good point about the Klingons enforcing a quarantine with force.

I’m pretty okay with just accepting it as a design change, I only bring it up because they previously tried to explain it.

Absolutely! Highly recommend watching DS9 :)

The reason why I say the Klingons "changed" and it's not just a design characteristic is when the crew of DS9 goes back in time to the tribble incidence on board the enteprise, a character (I believe Odo) asks Worf to explain why the Klingons then look so different from him. He gets agitated and refuses to talk about it. If I recall as well, Afflication, the ENT episode has a story indicating that something regarding Augment experimentation resulted in different looking Klingons.