give me an example
you just said
what specific policies
EDIT: and while you're at it
explain that, too
what do you mean
what decline, in what way
I already gave you two - public healthcare options and immigration policy. When Barack Obama took office, his idea of policing the border was continuing with the previous programs of erecting physical barriers in the form of fencing (128 additional miles were constructed, if I recall). This idea had wide-spread support among Democrats, including big names like Schumer and Feinstein who supported the act. This position has reversed completely under Trump. The same can be said about other policies surrounding immigration - President Obama is the president of DACA, but he was also keen on deportation. Approximately 2.5 million people were removed from the country between 2009 and 2015 via immigration orders. This idea, again, has completely reversed - now the talking point on the left is "Abolish ICE", which is an extreme position.
The same can be said about law enforcement. President Joe Biden started his career as the "tough on crime" mastermind behind the 1994 Crime Bill. In fact, it was one of his crowning achievements, it was created with input from minority community leaders who were concerned about a drug epidemic in their neighbourhoods. Both positions are reversed also - we regularly hear calls to "defund the police" and the prevailing opinion among Americans is that perhaps legalisation of some, at least "soft" drugs is in fact the answer here. Defunding the police is an extreme position - Michigan learned that first-hand as they recently "refunded" the police due to a sudden spike in violent crime. Legalisation I can roll with - I'm all for people being responsible for their own choices, even those that are self-destructive.
In terms of healthcare, President Obama advertised ACA by saying that "you can keep your doctor", it was created with both a public and a private sector in mind - private for those who can afford it, public for those who cannot. This is not adequate anymore - the core concept behind Medicare for All is a universal, public healthcare system for all citizens with the private option pushed to the side and concerned with elective surgeries, if not obliterated altogether, depending on which plan of some of the 2020 primary frontrunners you look at.
Just a few months ago Joe Biden happily proclaimed that he owns "a shotgun" (even though he doesn't know how to use it as I distinctly remember him saying that one should blast potential home invaders through a closed door or discharge firearms into the air indiscriminately to scare intruders, both being highly irresponsible) and isn't interested in attacking the 2nd Amendment. Come to find out, the administration is working on *another* "assault weapons ban". Oh, and who did Joe want to put in charge of gun control? Beto O'Rouruke, the man who gleefully supported gun *confiscation* from the debate stage. That's another reversal, in my mind. Nevermind the fact that these new policy prescriptions concern rifles - the least-used weapon in terms of homicide. The single type of firearm responsible for the majority of deaths on American streets is the handgun, but the administration won't tackle those as anything short of a national arms registry would be inadequate in tracking each and every one - there's simply far too many, so the good old AR will be the scapegoat du jour instead, at least for now.
These are just some examples, but there are plenty, really. Of course not all of those new positions are bad - in fact, I support some of them, to an extent. Some of them can also be explained by the nature of progressivism - it "progresses" with no clear end goal, however there's a line between what is a sensible measure and what is an extreme one. You can, in fact, progress "too far" and forget what exactly you were trying to fix in the first place.
I'm quite happy to support my positions as long as the discussion is civil and to-the-point. My point, in case the hyperbole was too difficult to digest, is that the increased reliance of government and obsessing over personality instead of substance is detrimental to political discourse. Jumping up in arms at the first sign of criticism is cult-like behaviour to me, or government worship. That might be a rough term to some, but that doesn't affect any of the key takeaways.