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 
How many other Science Fiction properties out there sprung out of a low budget TV show from the 60s but are still producing content in the same continuity without some kind of explicit reboot?
Star Wars is the classic comparison in all sorts of ways, and for better or worse Star Wars avoids this problem entirely by 1) having a much higher budget relative to the number of sets and costumes required for it's initial installment, 2) having picked an aesthetic that is crude, gritty, and seemingly practical which escapes looking dated many years after the fact, and 3) not being set in our future where the advances of modern tech make obviously retro elements look ridiculous.
Doctor Who has faithfully recreated sets, props, and costumes from as far back as the 60s as recently as 2017. Continuity is a different story - there's literally no doctor who canon - as the constant time traveling impacts things. Even the smaller TARDIS exterior from the Classic series is referenced as an actual, visual difference by the revival series. The current powers that run Star Trek would just pretend it was always that big.
I'll never accept the idea that it's okay to update a design but not properly reboot it and set it in a completely different and seperate continuity just because what you're making a spin-off of is old enough that it doesn't deserve to be treated legitimately. How many more years before the crude, gritty aesthetic of Star Wars suffers the same fate as the crude and campy aesthetic of Star Trek?
Whole series of television shouldn't be ignored by their own spinoffs just because their set designer and marketing teams decided something was lame or uncool.
People complained about exactly that during the Prequel Trilogy.
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.