so there are definitely some things I'm ignorant too.
Forgive me for asking but are you aware you can adjust the rear shocks? Five positions, see manual.
Then there's the tyre pressure to be observed. See manual.
You could also check by pushing the rear down and up and see if both shocks functions as they should. I once had a rear shock that had become stiff. Turned out a long winter on the center stand had dried out some rubbers inside. It was not a genuine Honda shock but a Koni. Although I had bought it many years before, Koni rebuilt it for me free of charge.
Those of you that have motorcycles on the centerstand in winter: do not forget to pump bike up and down occasionally.
Could also be you're not that too familiar with riding a CB500/550. Especially the 500s were Spartan in their ride. For us in Europe it was OK, but Americans are used to soft matrasses on wheels.