Jellico didn't push anyone beyond their limits. He pushed them beyond their comfort zone. As was later seen when Data explains to Geordi exactly how the captain's orders could be met
Many times during Picard's command, the crew needed to work extra hours, & achieve what seemed nearly impossible. They were willing to go that length for Picard because they trusted him from having built a relationship with him. Jellico had to demand that level of performance even though he had not yet had that opportunity. He had to just expect that it was "Starfleet's Finest Crew" & therefore they owed him that much, because they owe it to Starfleet, especially with the safety of the Federation on the line.
Riker was wrong in that he believed himself to be too important to be just a piece of the mission, instead of one of it's architects, who had a say in what should be happening. He succumb to hubris. (Not the 1st time for him, btw) He needed to be thinking his way through the difficulty & looking at it from all perspectives, instead of just becoming resistant
Excerpt From Ensigns of Command
PICARD: How are we progressing, Mister LaForge?
GEORDI: About like you'd expect. (Not at all)
PICARD: Splendid. (Do it anyway)
WESLEY: He wants the impossible.
GEORDI: That's the short definition for "captain."
Odd that he forgets that being the case, when the captain isn't Picard. They worked their asses off in that episode, & no one bitched to the point of being relieved
People are much more willing to bend over backwards for someone they've had a longterm working relationship with. LaForge had been serving with Picard for more than two years at the time "Ensigns of Command" originally aired. Riker says as much during his confrontation with Jelico: "You don't inspire these people to go out of their way for you, and you've got everyone wound so tight that there's no joy in anything."
Additionally, Scotty spent the initial moments of the travel pod ride to the Enterprise
in TMP complaining about the difficulties in having the ship's launch moved up becuase of the V'Ger threat, only to completely change his tune once Kirk informed him that he, not Decker, would be commanding the mission.