Earlier quoted context omitted.
I use reducing the rate of incoming tickets as the primary OKR for on-call engineers. Has never failed to reduce that burden over time. Just like you say - I'm convinced it's the only correct strategy to make the problem go away.
if you set a goal but don't empower people I think overall you end up killing morale. IMHO, reducing the rate of the incoming tickets can only be done with investments that are not fire-fighting. If you're doing that I think it's awesome.
If there's too much firefighting, that means we owe additional support to the team or need to rebalance other work appropriately in the interim.
The opposite is also true. If we don't have too much firefighting or valuable de-risking to do, we can take on more product work.