The Aston Martin driver finished third on track, negating an initial five-second penalty for lining up incorrectly in his grid position at the start.
But, after the podium ceremony, he was given another 10-second penalty for work starting on his car when the first penalty was served in his pitstop, dropping him behind George Russell and to fourth in the final results.
It duly denied Alonso his 100th F1 career rostrum, but rather than argue with the decision the Spaniard was frustrated at how slowly the penalty arrived given he pitted on lap 18 of the 50-lap race when the incident occurred.
"I think today is not good for the fans, when you have 35 laps to apply a penalty and to inform about the penalty," Alonso said.
"You wait for after the podium, there is something really wrong in the system, but it's the way it is.
"I feel sorry for the fans. But I really enjoyed the podium. I had the trophy, I had pictures, I celebrated with the champagne and now to have 15 points or 12 points it really doesn't change much for me.
"But it's a bit sad for the FIA."
Alonso felt the FIA must speed up its penalty decision rather than overhaul the process, as he felt had he been told about the 10-second penalty during the race he could have pulled out a bigger gap over Russell in a bid to keep third place.
"I think it needs to come back to common sense. We don't need to invent anything," Alonso explained.
"The thing is that they told me you have five seconds penalty. So I push a little bit harder. And I open seven seconds and I pay the penalty. In the second stint there was no investigation, no information. No nothing.
"If someone tells me you have 10 seconds I open 11 seconds."
Alonso did hold his hands up for the initial penalty for being outside his grid box and wants to review the onboard footage to avoid a similar incident.
"I need to re-watch the race. But apparently I was too much on the left," he said.
"So it was my mistake I need to pay more attention to that is a little bit also strange that in two races, two cars, Esteban and myself. We have similar things.
"So maybe this is cars, or the Halo, whatever it is interacting with the vision of how we position the car. But anyway, that was my mistake."
