I guess it is eye-watering for some pilots when they realized that they are expected to quickly master procedures, maneuvers, and knowledge of a company and aircraft they've never seen.
Unlike the local FBO or flight school, airline training courses aren't set-up to spoon-feed a trainee. For low experience pilots, it can be a huge challenge.
As always MASTER:
Aircraft Systems
Limits
EP checklist memory items
Callouts
Profiles and maneuvers
Fleet SOP
Flight Operations Manual
If you nail the above items early in training, you'll have some processing power left over to absorb technique and work on rough spots. Airline training is about filling the required FAA training square and getting a pilot onto the line ASAP (at the lowest cost). This pace can be overwhelming to the new guys who aren't expecting it.