If you only ever experience 0 to 2 with a baseline of 1 then that's no different experientially than -1 to 1 with a baseline of 0. Since baseline is going to be the 'normal' experience it's going to be routine in both cases. Whereas they'd be confused talking to one another as the overlap of baselines is at the most positive and most negative positions versus one another.

Basically if we were to go through life only experiencing pleasure would less pleasure basically be pain if you had no capacity to feel or understand pain.

Plus the whole idea that pleasure and pain are a continuum seems overly simplistic.