Wrong forum for this question, but peonies should be planted in your zone with the buds barely an inch below the soil. Any deeper they'll grow but never bloom.

It took mine 4 years to bloom. The first year,they looked like yours do now. The following 2 years they had more and more leaves but no blooms. Finally they bloomed this year.

And I agree that they should barely be covered with soil when planting.

Sorry. Not sure how landscaping snuck in there. I'm relived to hear this is normal. All of my neighbors have these full tall bushes and I'm like what gives? Thank you!

Peonies are slow growers and it usually takes them a few years to get to the full bushy stage, they should get better year after year

It also depends on how big the root was that you planted originally (e.g. number of eyes, feeder roots, etc.)