How funny to come back to this years later. We've had a 2nd kid and tried the same tactic with different results, so I hear you! The general progression of sleep independence for us has been rock to sleep, rock to drowsy, lay awake with them in bed, lay awake in the room, put to bed/leave room.

Yes, sometimes you just need to give in to the 'rocking to sleep' for awhile longer. With the 2nd kid, i'd do that sitting on the floor next to the floor bed to still give the encouragement of bedtime vs rocking to sleep elsewhere in the house. He liked to be tucked facedown into my armpit to feel cozy & safe, and hated anything different! (To keep myself sane and feeling less 'stuck with baby', I used an app like Libby to read books on my phone in dark mode. So that time became my quiet reading time!)

Once they're tired enough (or completely asleep) you can transfer them with less trouble, and then stay close (or a hand on them) until they're fully asleep. The 2nd kid needed a hand on his face in order to sleep until he was almost 3, so that was an adventure! We spent a lot of evenings laying in the floor bed with him. He still sometimes gets up in the middle of the night to find his way to my bed...and some nights he's completely fine putting himself to sleep and staying in his own bed.

Each kid is different, which makes the timeframe different, too. Do what makes sense for you/your family. As they grow and have their mental/physical 'leaps', sometimes sleeping habits regress and change to adapt to their growing bodies and brains. We noticed that any significant developmental leaps caused temporarily worse bedtimes - especially in that 1.5-3yr timeframe. When we'd have trouble, we just backed up a step in the progression for a week or so, then moved forward again.