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 point is though that DW confirms again and again that how things looked is accurate. We see a 70s Cyberman helmet in 2005, before we see the Modern Cyberman. We've seen the Dalek redesigns happen, and past designs all the way back to the 60s reappear.
Sontarans are a clone race, so its not difficult to imagine changes happened to their process or gene template over time. Perhaps one day we'll see a mixed Sontaran fleet with the short stocky guys from Series 4 and the taller ones from Classic Who and Chibnal. Perhaps Silurians have different subspecies. Those are easy, one sentence explanations, that don't rely on scoffing at old SFX and going "well its broken already anyways".