while I agree with this, I am now curious what you are running in 5e and what in SD (and what your pages of houserules are…)
The most immediate examples:
My coworkers want to play in a Lord of the Rings-style (but not Lord of the Rings) D&D campaign, which 5E's heroic fantasy tones and options fit quite well. There's war (over the horizon initially, but not forever), but the game won't ever focus on misery porn, but rather the idea that the forces of Good can ultimately triumph over Evil.
This weekend, for a different group of friends, I'm running a Shadowdark adventure I don't want to say too much about (/wave to those here), but it bounces between several types of horror, there's a high likelihood that people will need to use back-up characters to replace the first line when they die, and "victory" mostly consists on getting out alive, ideally with at least a little treasure to show for their efforts.
Now, it's
possible to run each of those adventures with the other system, but the system fights against it. Horror in 5E mostly has to consist of deactivating all the player options and throwing unkillable threats at them. Heroism in Shadowdark means giving players more options and power than they normally have (like not having darkness be extremely dangerous for them) and finding a way to reward them other than just for gold pieces collected/spent.
I would rather match the game to the adventure than have to do surgery on the game to make the adventure work.
I don't think I'm using any house rules for either game currently, other than making up a few monsters and spells as appropriate, as folks who follow my posting history might guess.