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?
EDIT: PEOPLE I SAID WHO'S WITH ME NOT WHO ISN'T CM'ON 
The whole deal with that is that they did it, in TOS, without any sort of explanation. We just had that dude, who McCoy discovered was really a Klingon, even though he looked just like a human. That whole thing is just adding an explanation for something that was long-since already there.
Also, you sound like you're talking about the Orions. Do Klingons even have scientists? Somebody has to build the ships!
There was also a Klingon scientist in the Enterprise 2 parter about how the Klingons got smooth heads. He even talked about what it was like being a scientist in a society of warriors.
It's also something that literally happened in a TOS episode that almost everyone saw and liked.