I'm a qualified Facebook ads manager. Changes to Facebook's algorithm have certainly altered performance across many accounts. For the accounts I manager, May has been the best month by far since the first major changes in January.
Have you put Facebook's recommendations for their new measuring tool, AEM? Is your domain verified and is CAPI all set up?
For accounts where I saw performance decline dramatically, I rebuilt campaigns, rebuilt lookalike audiences and have started testing again. I have found the CPMs for all my lookalike audiences have increased, but broad and interest based audiences are proving cost effective.