The website is bad, but phoning Amtrak actually worked pretty well for me! There wasn't much of a wait, the staff were friendly and knowledgeable, and they were able to really quickly plan out complicated routes with multiple transfers and compare different options. (One wonders if they could make whatever fancy planning/booking system they use available to the public.)
Admittedly this was a couple years ago, so it's possible COVID or budget cuts have changed things for the worse.
