It does have bias, true, but you can deal with bias. You do pinpoint studies to measure it and use them to correct bigger trends. You compare with the overall mortality change. And once you have an estimation of the bias, you can apply it back to the overall mortality numbers and get a much better result.
So if someone is a heart patient, but they got COVID and their condition suddenly worsened, the death certificate might state the cause of death as heart failure from the existing condition with COVID as a contributing factor.
People who had COVID but died in completely unrelated ways, such as from car accidents, are not counted in COVID death statistics and don't have it listed as a contributory cause in their death certificates.
Unfortunately, we mostly see one-sided criticism.
Edit: Thank you for downvoting without commenting!