Doesn't have to be railroading for this sort of thing to occur. You can't out-plan effectively infinite options, and it's important to set a baseline of expectations not only of the DM but also of the players.

Shockingly, some players don't understand the basic "find a reason for your character to travel with the others" concept unless it's spelled out to them. There's also some players that will intentionally play as though they're allergic to main plot threads, which can be fine if that's established going in but a pain in the ass if there was an understanding that the DM might be able to prepare shit in advance and not always instantaneously adlib.

Like don't agree to Descent to Avernus if you don't have any intention of going to Avernus.

Sorry, I get you were probably joking, but I've also been in some groups that just didn't work out because players weren't straightforward about what they were looking for.