Mars's Valles Marinaris is 10km deep in some places, but it's also as straight as a rule and wide enough that if some of these moaners came across it in ED they would say it was pants.
Horizons had this problem when it launched. FDev desired to go more realistic with the planetary gen, and the result was more realistically coloured planets with less exaggerated and gamey features and colours. They backtracked and we got this:
Truly flat ice-rink surfaces, crazy colours, and exaggerated height maps just like the original ED (but with copy-pasta, GPS marked, same-as geological and biological fields). So they had to change it for the vocal, review bombing, racing crew.
Now FDev are trying to introduce a completely new Planetary tech and it's got massive potential, and the vocal, review bombing, racing crew are furious that their toys are being taken away and our pointing to the lack of optimsation as a way of leveraging their opinion over the thousands of less vocal solo explorer players who are happy to see this grow.
So, because they have an end-game in sight, even when confronted with encouraging and reasonable shots of planetary tech, they, out of pride and a sense of purpose, will not concede to any point. At which point, it's not even worth talking because all they hear is "blah, blah, blah, not Horizons."
So I don't care if you don't like it. Go play SC or space engineers or Kerbal Space program. One thing is for certain, you'll be back.