100% agree.
But, what it means in practical terms is that I can never use any planar sourcebooks. I have to make everything up 100% on my own. The Planar stuff is almost never self contained. Importing, say, a module from Forgotten Realms to Dragonlance isn't generally that hard. Yes, I have to make changes of course, but, I can certainly use large chunks of that module. The planar stuff is just so strongly tied to all the other planar stuff that I've almost never been able to adapt it. Personal failing on my part, but, after the third or fourth attempt, I've just thrown up my hands and completely ignore all of it.
IMO, if you don't like the default lore don't use it. I'd rather have a set of lore that is the default than have none at all. Furthermore, traditional D&D lore shouldn't be something the game should just abandon, that would only upset the fans. I know I was rather upset with 4e for that very reason. It's one thing to change the mechanics, but it was a slap in the face to scrap all the lore I cherished and invested in over the years.