I am the kind of person who enjoys “big weird” scifi like Stanisław Lem. Stories about trying to relate to and find common ground with something so alien that the prospect of even understanding is basically hopeless. Star Trek usually doesn’t do stories that, which makes sense as it often uses alien races as allegories or stand-ins for real-world human relations.
That said- I thought those early Klingons were super weird and scary because they were just so alien. It really made sense thinking about how it took a century before they could get to the events of Star Trek VI, and it made the Khittomer accords feel like so much more of an accomplishment. Like- you made a treaty with WHAT?
And just aesthetically their ships and armor looked like something out of HP Lovecraft or HR Geiger:
This is not to say I dislike how Klingons were portrayed previously, kinda like Mongols in TOS or Vikings in DS9, just that they never felt scary to me. They never felt like warriors. I was never afraid for the gallant crew of the Enterprise D (a science and exploration vessel) going into battle against Klingons. But I really enjoyed the alien-ness Disco tried to go with. Anyone else with me?
To give credit where it’s due, RotS and many of the Disney-era Star Wars products have gone a long way to fitting the glamorous, shiny prequel aesthetic into the gritty, used, “lived in” aesthetic of the OT. I’m not the biggest fan of The Last Jedi, but I actually think the implicication of the shiny galaxy just being a property of the rich inner rim planets was a great move in unifying everything.
There’s also the idea that the Empire mass produced everything to a cheaper quality which lead to less frills and faster decay. Supposedly The Acolyte show is gonna extrapolate from this further, and is set like 300 years before the prequels.