Bunny Doesn't Chew

My rabbit (10M) has never had a ton of interest in chewing. He eats a primarily hay diet and has for as long as I've had him (about 9.5 years), and he's never had any dental issues in the past. However, in his most recent vet visit, the vet noted that his molars were long. Not long enough to be a concern, but still.

He has constant access to a multitude of safe chewable toys: cardboard, wood sticks, wood pucks, wicker-style wooden toys. I rotate them weekly. He will occasionally give them a grumpy nibble when they're in his way, but he otherwise ignores them.

The only material he'll consistently chew is very thin cardboard. He's otherwise very healthy, and he's never been much of a chewer, but I am concerned. Does anyone have picky rabbits and tips on how to entice them to chew?