So a simple ask. What do people feel they learn from running other games? Actual concrete examples, not vague "different ways of doing things"
From Ironsworn, I have adapted the entire exploration system from Ironsworn into my D&D game in order to make exploration much more exciting and fun. And it has worked very well. My Out of the Abyss game would be far less enjoyable for the table if I ran it D&D RAW as it was written in the module.
From 3:16 Carnage Beyond the Stars I have in the past incoporated their system of developing characters through flashbacks which allows the players lots of flexibility in expanding their characters into the setting.
From ... a damn, I'm blanking on the name of the game - you play a character in medieval europe who is playing a character in medieval Europe. So, basically, you're playing a medieval version of a D20 Modern game, only imagining that you are in the middle ages. It's all a bit meta. Anyway, they had the idea of Backgrounds, which is something I've used in many other games. In this case, Backgrounds doesn't mean where your character comes from. This means that the player can choose parts of his character to be placed in the background. It's true and it exists in the game world, but, the DM is not allowed to affect it or use it as a plot hook. I'm explaining it badly, but, for example, if your character had a horse, you could background the horse which meant that it never becomes a problem. It's never stolen, it is always available, it's just... in the background.
Sufficiently Advanced has a fantastic skill resolution system that incorporates different time scales - a very early precursor to the idea of Clocks in other games. Haven't really adapted it yet, but, I do tend to loosely use the framework when dealing with things in D&D.
Those are three examples off the top of my head. None of these things would have occurred to me had I not spent some time wandering through systems from time to time.