Yes Amtrak has it's problems, but I wouldn't put it in the useless category either for bike touring. Every once in a while I need to anticipate a delay but otherwise it serves a purpose.

I've used it in two general models:
(1) Long distance one-way for not too much when it connects where I want to travel. In last five years I've had five of those trips:
2018 - train from Austin to El Paso. Cycle home.
2018 - train from Minot to Chicago to Austin after driving to Abilene and cycling to Minot
2018 - train from Austin to Texarkana. Cycle to Memphis. Rental car to Memphis and train back to Austin
2019 - train from Austin to Tucson. Cycle to El Paso. Train back to Austin.
2021 - rental car Austin to Albuquerque. Around ABQ a few days with my bike. Train to Chicago. Around CHI for a few days. Train back to Austin.

(2) When I was in a city with a regional route to cycle on part and take a train the other part. When in Portland, I did all the variations of Seattle to Portland, Vancouver to Seattle, Eugene to Portland, Salem to Portland many times on the Pacific Cascades. When I lived in San Jose, I did the SLO back to San Jose four or five times.

I haven't had much issues with employees or customer service in my travels. I've seen occasional long delays (more on long haul routes than short ones) but generally structured my travels so they adjusted.

For most all those trips, Amtrak was a better alternative for me than others either because of cost or ease (e.g. packing/unpacking for airlines - or ability to make short term tickets or one way). In return, I structured my trip keeping in mind Amtrak routes and anticipated some uncertainty in schedule.