It seems reasonable to speculate that younger people are able survive longer with respiratory problems and probably have less co-morbidities.
In the same way, COVID puts pressure on the hospital system as a whole. Nurses who could have been monitoring a post-surgery recovery are instead monitoring ventilators in the COVID wing, or are quarantined after being exposed. The crash cart arrives a little bit slower to a heart attack, because the closest one was already in use. If the available nurses are on longer shifts, that contributes to sleep deprivation, making it easy to miss details that would otherwise have been caught.
This is true across all age groups. As of September, while COVID had 4.6 million direct fatalities, there had been 15 million excess deaths. Determining the final scope of COVID will be a matter of long research, and certainly isn't something that can be resolved in a short internet argument. Dismissing it as "Seems unlikely." when not even comparing between the same same type of measurement seems premature.
[0] https://www.wsws.org/en/articles/2021/09/06/econ-s06.html
There’s definitely a significant rise in excess deaths among 25-44 year olds coinciding with the Delta peak in August/September.
Something interesting though: In the Covid “valley” of June/July, when Covid-related deaths were at a record low nationally, 25-44 year olds still had a ~35% increase in excess deaths. I’d expect a drop in excess deaths close to prepandemic levels if they were being driven mainly by (short-term) Covid effects during that time. It seems like the baseline death rate increased independently of number of active Covid cases.
Covid deaths were accompanied by a steady increase in overdose deaths starting in early 2019 (https://www.cdc.gov/nchs/nvss/vsrr/drug-overdose-data.htm), rising from from 68k to 97k over the course of the pandemic.
I don’t have time at the moment to do the math, but I’d suspect most of the increase we’ve seen in the past year is due to Covid, but with the increase in overdoses and other causes contributing much than noise since 2019. This could explain the higher death rate that persisted throughout the summer.