There are indexes that invest equal amounts of money into all companies, so Nvidia doesn't dominate. Or you can pick low growth high dividend indexes to insulate against AI. Or just grab Vanguard LifeStrategy if you don't want to think.
The current situation is unusual. No index can handle all situations. Either adapt or use a fund that does the thinking for you, right?
If the US does something to destabilize the dollar, will economists be running around saying “the dollar was never intended to be used for that purpose!”? No.
It doesn’t really matter if the index “wasn’t supposed” to be something it became. The problem is the same. The only difference is who you blame.