https://en.wikipedia.org/wiki/Undercounting_of_COVID-19_pand...
The chart on https://www.cdc.gov/nchs/nvss/vsrr/covid19/excess_deaths.htm shows all cause deaths before and during the pandemic; there's an extremely clear difference, and it coincides closely with the spikes in COVID cases we've seen.
This method of reporting avoids all the complexities around "died with COVID" vs "died of COVID", people who never get tested before dying, etc.
Aren't there about 100 other confounders that could be in the mix there
I can give one example, which happened to my dad...
"Sorry, we have to reschedule that surgery to remove the tumor because we're anticipating a covid spike and need the bed availability."
Repeat until he died due to cancer spreading.
See the chart about 2/3 down on https://www.healthsystemtracker.org/brief/covid-19-continues..., titled "Average daily deaths in the United States, by cause (2020 - Present)". We don't see a massive spike in other causes of death (including cancer, which is a flat line at ~1,600/day throughout), and no one's likely to misidentify a cancer or heart attack death on a death certificate.
There are certainly cases like your dad's, where delayed screenings and treatment had individual impacts, but none of the stats available to us show this explaining a meaningful amount of the 1.3M excess deaths observed.