I am in complete agreement with your analysis here. I fully agree there is a double-standard of expectations, and quite frankly has been, for well over 2 decades.
The question is: what do we do about it?
I watched every single day of the live coverage of the January 6th Hearings that went on throughout the summer of 2022. I watched the Impeachment hearings. I watched the Charlottesville reactions. I watched all the coverage of the criminal indictments and the criminal conviction. I've seen quite a bit on Project 2025 long before Biden's catastrophic debate. The problem is: truly, nothing is sticking. Why? Because right-wing media largely controls the narrative in this country, both thanks to the injection of billionaire money and corporations, but just the prevalence of unabashed conservative media, ranging from church and AM talk radio to Fox News on in every breakroom and doctor's office waiting-room in the country. They muddy the waters so effectively that no matter how loudly we point to these problems, they have talking-point to deflect, downplay, or muddy the waters of reality... And uninformed gullible apathetic voters lap that shit up.
The only thing we can really do is not make it easy for them. We can't give them an argument that actually has legitimate substance to it, like Biden's age and cognitive capacity. Look, to me the data is clear: 75% of Americans don't think Biden is fit to run again, and that Democrats would have better odds at defeating Trump with someone else. I'm in agreement. Every single data point I can find signals Trump sweeping the election. Mostly because the guy who supposedly holds the moral high ground can't shake his ego and step down for the greater good.