People were accepting bitcoin for payments under a flawed assumption that a zero-confirmation transaction was in some way "secure," despite this not being enforced in any way by bitcoin's consensus rules. The introduction of RBF made it clearer to people who had made this bad assumption, and they revised their policies about accepting unconfirmed payments.
ATMs are still around, and growing in number, but they seem to be getting more expensive to use. See coinatmradar.com. There are magnitudes more now in 2020 than there were in 2015.
> As the mining difficulty has increased, more people are genuinely concerned about the carbon footprint.
People who think this need to ask themselves: "what can I do about it?" The answer to this is absolutely nothing. People are going to mine bitcoin, and you're going to have to get over it, because you can't change their decision. If it is inevitable that people are going to mine bitcoin, then rejecting bitcoin because you don't agree with that is simply self-harm. You are foregoing potential benefits (of price appreciation, technological improvement, etc) because of a religious-like belief that humanity would be better off using less electricity. (Ironically while spending half the day in front of a computer, having a TV in every room, carrying a smartphone around 24 hours a day and cooling down with the aircon.)
> I've seen more pessimism about scalability, as off-chain solutions have failed to meaningfully materialize.
They are materializing. The Lightning Network is running now, and improving frequently. I suspect people who are pessimistic about this have not actually attempted to run their own node yet and are waiting for adoption to grow first. Kind of reminds me of people who were waiting for Bitcoin adoption to rise in 2011, and failed to capitalize on an enormous opportunity.
> Post the big bubble of 2018, the public Bitcoin "brand" is basically tied to get-rich-quick scams and ransomware.
It was associated with this way before 2018. When I first heard of it in 2011 it was being branded as a ponzi scheme. It was tied with the silk-road for buying drugs. WannaCry was just the case that brought it to more people's attention.
Bitcoin is still doing as it always was, and in many ways it being distinguished from other get-rich-schemes (known as shitcoins), by focusing on the fundamentals of its finite supply and network effects. The shitcoiners are doing bitcoin a favour by dissociating themselves with it and trying to promote their scams.