If those first level PCs want to hunt down an arch-demon in Avernus, they're free to attempt it in my campaign. On the other hand, 20th level PCs don't get hired to take out the rats* in the basement in my campaign either. So I fail to see your point. If you want the PCs to be challenged, you have to design encounters with those PCs in mind. I don't see why that would be controversial.So much for "the world doesn't level up to match the PCs"...
*It's never really rats.