I would start over. I just took out a marionberry that never has done much. Bought at Lowes when I was a newbie gardener. Didn't realize it was for zone 6.

I have lots of raspberries if you are in the Denver area and want to try something new.

I'm starting to wonder if I dropped the pH to a 5.5-6 would that inhibit foliage growth and stimulate flowers and berries? I know friends and neighbors who basically neglect theirs and have plenty of berries every year. I'm stumped. I might try loading up on the peat this fall and seeing what happens next year. If nothing, then it's going away!

If I'm not mistaken, all raspberries bear fruit on second year canes, so if you're growing only new canes every year (due to pruning and/or die-back), that's the reason you're not getting any fruit. pH, fertility, etc., have nothing to do with it.

Can you try protecting some canes over the winter to avoid the die-back? You can look online for techniques, but I seem to remember seeing recommendations to lay the canes flat on the ground and mound compost, dry mulch or even dirt over them for the duration of the winter.

Needless to say, getting new plants from a local gardener might also work. Most raspberries spontaneously tip-layer so readily that there are lots of new plants to go around.