Q.Why won’t my raspberries grow taller? They stay about 8 inches tall.
They are good berries, highly recommended but don’t grow over 8 inches tall. The name of them is Heritage.

Certified GKH Gardening Expert
It's important not to crowd the bushes with other vegetation, and it's a good idea to mulch the plants. Have the plants been fertilized? Also, check the soil. Is it compacted? They prefer sandy loam soil with lots of compost and a pH of 5.8 to 6.5. There must be an element of care that is missing. Here is more:
https://www.gardeningknowhow.com/edible/fruits/raspberry/when-to-feed-raspberries.htm
https://www.gardeningknowhow.com/edible/fruits/raspberry/care-of-raspberry-plants.htm