This is what I would guess as well. Microbial competition.
COVID-19 and the Flu | ASM.org
The American Society of Microbiology predicted an uncharacteristically low flu season ~1 1/2 months ago. It also isnt isolated to NA but has been the trend globally with the southern hemisphere now out of their flu season.
Other resources also include co-infection as a reason for lower flu numbers. Basically since the pathway of infection and symptoms are similar, it is likely that COVID is masking the flu in people who have been co-infected by both. Since COVID is much more virulent and contagious, it is more likely to have COVID without the flu than the flu without COVID.
Who cares that the tests have poor accuracy. It is better to be overly cautious than loosely cautious.
What I have noticed during the pandemic is a lot of people fear and emphasize the wrong things. Yes, everything you have been saying is accurate. The number of positive tests and deaths due to COVID are likely inaccurate, yes lockdowns are relatively ineffective, yes a rushed vaccination is scary.
What people fail to consider are the indirect or delayed ramifications.
With a novel virus we have no idea about the long term troubles that may be associated with it. Yes 90 whatever % of people survive, but what about 10 years from now? HIV, HSV, VZV are just some examples of viruses that remain indefinitely, HIV and VZV becoming more serious long term. Multiple resources show that people who were infected with SARS in 2003 have had long term respiratory impairment, some as serious as pulmonary fibrosis
The other issue is the changes in protocol and overcrowding of our hospitals leading to poor treatment for more emergent patients. At its peak major hospitals in Texas had overwhelmed ERs and people were dying from routine non-COVID related issues while waiting/searching for available doctors.
Another example, TGH in Toronto, the countrys largest transplant program, limited transplant surgeries for a month at its peak this summer to re-allocate resources (ICU beds) and because COVID infected organs may cause issues in immunosuppressed individuals.
People need to start looking at the bigger picture.