I think memory management on modern phones is good enough that running apps in the background is no longer an issue. Provided you're not using a piece of shit.
I've trained everyone in my personal support range to restart their phones and tablets weekly. Flushes out all the apps and noticeably reduces complaints and questions from the users.
There is a difference between running in the background and being in memory.
Recent Apps may or may not be in memory, that's why when you switch to a "recent" app not used in a while it restarts anyway instead of continuing where you left it, it's effectively just a bookmark to a closed app. So the list being long doesn't mean these apps are using memory.
While running in the background is unrelated, apps can run in the background regardless if they are in the Recents list or not. And it can absolutely cause issues or excessive battery usage, but clearing the Recents list is not the solution.
The meme betrays a fundamental misunderstanding of how mobile OS work. They’re not “running in the background.” If they haven’t been interacted with recently they have been frozen and moved out of active memory. Tired literally just looking at a picture of an app when you go to the task view.