I feel like that's a Third-Way philosophy and not exactly the truth with FDR being such an obvious counterpoint. I generally don't agree with it just from having seen reps at virtually every level rewarded when they do something the constituents that they represent actually want and support (ie: Sawant beating the recall effort). On the opposite end, I've also seen reps enact legislation that is good for people but which constituents don't support for one reason or another and have that backfire (I can't remember the Republican's name, but he passed a bill for vets with bipartisan support and got ousted for working with Dems lol).
Nah, I got really into this stuff around Bush 2 (earlier but not with enough comprehension to brag much on it) and it was going strong. I remember this even during Obama:
Why the First 100 Days Matters
Here's a clearly liberal media example:
https://www.washingtonpost.com/wp-srv/politics/obama/100days/index.html
Here's one that does the last three presidents:
BIDEN'S FIRST 100 DAYS: Charts show how they compare with Trump's, Obama's, Bush's, and Clinton's
I remember seeing one of Obama's strategists' saying that they screwed up by not broadcasting his tax cuts (particularly payroll related). It's definitely a combination of making sure the people feel the impact and know who's responsible. The problem with your examples are they aren't felt. The COVID relief was good, but on expiration dates. The infrastructure deal isn't being felt yet. The poll numbers reflect this clear as day and I'm skeptical that the Infrastructure bill will be enough to turn the tide, feel free to disagree because that's purely my speculation.
He had another year and month, which sounds like a lot but if legislation is passed that isn't felt then it will fall right into the paragraph above. They need to make moves that Americans can feel and recognize as "thanks to the Dems." That'd actually be easier with a couple of executive orders. Dude could probably make up a ton of good will by just legalizing weed federally or using executive privilege to pass one or two promises that are within his power to do so. Either way, I don't see the evidence that Democratic leadership has done well strategically when we talk about winning elections and I also think their efforts to help the people have been harmfully neutered by the likes of Manchin, Sinema, and the worst of the Blue Dogs. It's not the progressives holding up legislation, even if that's what some of the more radical lefties were rooting for. If the polling doesn't flip, it's gotta land squarely on the shoulders of the centrists. No passing the buck to Progressives that even sacrificed some credibility with their most vehement supporters in the name of getting that Infrastructure bill passed at least.