The bedtime handoff, one small step at a time
Falling asleep alone is a skill your child builds in steps, not a switch you flip. If you've become the cue that means sleep is safe, the way through is to gradually shrink your role at bedtime rather than removing yourself all at once.
Falling asleep alone is a skill, like tying shoes or riding a bike, it comes in stages, not overnight. If bedtime currently runs through you, the way forward isn't to disappear tomorrow night. It's to make your part smaller, a little at a time, until your child finds they can do the last bit themselves.
What's really happening
Some nights this feels exhausting, and some nights it feels like you must be doing something wrong. You're not. Needing you close at bedtime is how your child's nervous system works right now, at this age, kids regulate through the people around them. Your calm presence is what settles them; that's called co-regulation, and it's not a habit gone wrong, it's how young children are built. It also helps to know separation anxiety has its own rhythm, it tends to peak around 18 months, again around age 3, and again when school starts. Bedtime, when everyone's tired and the day is finally quiet, is often where that shows up the most.
Tonight you can
Sit beside the bed tonight, and go quiet once he's settled. You don't have to leave the room to change the routine. Start by changing how much you talk instead, stay close, but let the room get quiet once he's settled, so quiet becomes part of what "falling asleep" feels like.
Tomorrow night, move your chair one step toward the door. Just one step, and then leave it there for several nights before you move again. The pace matters more than the distance, staying in one spot long enough for it to feel normal is what makes the next step possible.
Say the same short goodnight line every time you leave. The exact words matter less than the repetition. A predictable line turns "leaving" into a known part of the routine, instead of something to negotiate over each night.
What not to worry about
Wanting you close at bedtime is ordinary at this age. It isn't a sign that bedtime is broken, and it isn't a sign that you made a mistake by staying close this long. You're not behind, and neither is he.
When to seek help
Nothing here points to a reason for concern.