I agree with what you are saying on a national basis. But some trains can make money; from what I understand, the NEC trains do well and make money for Amtrak. The problem is that off the East Coast, there are vast spaces between largely populated cities, and it’s usually more convenient to drive or fly.
Rail travel is fine, but intercity travel should be limited to largely populated cities are relatively close, but not close enough to make driving convenient: NEC, LA to SF, Dallas to Houston, etc. We don’t need a train from California to Florida. That’s stupid.