"Science is the belief in the ignorance of experts" - Richard Feynman
It is my impression that back in the day it was more common for academics with differing opinions to banter or at times straight up disrespect each other semi-publicly. This could be historical survivorship bias, but it is a fact that aspiring scientists had a much greater likelihood of becoming a tenured PI in previous generations, and usually reached that status much earlier in their lives.
I fear that with the state of the academic job market along with present cultural norms, it is less common now for an early career investigator to question the quality of an established PI's work, or even for PIs to meaningfully criticize each other in scientifically accessible formats.
Besides, questioning the work of past scientists is implicitly questioning the research of many modern scientists, at least if that questioning is to be considered remotely novel. There are socially acceptable avenues to question past science, but there are also cases where modern PIs of influence have built so much on an assumption from prior results, such that the impact of their work would indeed be threatened by questions of the foundation.
It is important that the latter situation is handled in a manner consistent with scientific ideals. I don't know what Feynman was exactly referring to with his quote, but I'd be surprised if he was focused on the behavior of random lay people. Someone immersed in science is probably going to be most concerned with the behavior of fellow scientists and emerging trainees.
Regardless, this is also a great way to stifle important scientific discourse. Nobody wants scientific commentary to happen hidden from public view, so more and more happens on preprint servers and social media. But then nobody wants to make even good faith criticisms because they don't want the general public to misinterpret, aided by bad faith spinning by other parties.
Of course you will see criticisms related to e.g. labor conditions, but when it comes to criticism of scientific practice or even in some cases specific results, there are always a bunch of people ready to comment about how most critics are quacks and we need to be careful about extremism. This is awfully convenient for the scientists that are doing subpar work.
Hard to say. It's hard to get a YEC to come out of the closet here. Maybe I'm a little overly sensitized to YECs in particular because I spent some time on the YouTube YEC debate circuit.
But it hardly matters. What matters is that there are a lot of anti-science ideologues out there, some of them are well organized and well-funded, they are developing a collection of stock rhetoric (including that Feynman quote) which can be very persuasive, and some of that rhetoric appears regularly here. Whenever I see it I try to smack it down, but sometimes it feels like whack-a-mole.
Oh, yeah, engineering and all the other practices are rooted on this.
Science is not.
(Unless by those things you mean the scientific method, because scientists usually practice that one.)
A scientist must be incredibly knowledgeable in some things so that they can advance the world's understanding in things that they're ignorant about.
They also must be willing to uproot their assumptions, if the evidence points that way. But they still must be experts in their assumptions.
There is a huge amount of prior literature on many topics, so to be an expert in something like immunology you're almost definitely a PhD, or maybe a very academically inclined MD. However this notion of expert simply means you have learned intricate details about many of the important previous results, most of which are probably true. It does not mean you actually have the ability to do good science in the field of immunology.
But for any technical question in your niche that isn't uncharted territory you can serve as an expert. Such expertise has obvious uses in many other domains, and as there isn't really a great term for it, it gets called scientific expertise. Perhaps the person may be called a biologist, but that also has scientific undertones which may or may not be warranted.
I'm sure you are aware of this, but I don't often see it explicitly stated, and so it feels like people talk past each other in a sense. It is wholly possible to approach e.g. chemistry in a non-scientific way, just as something like business can be approached in a scientific way. I don't think the double language will be resolved any time soon, since I don't see much effort to make this distinction in the actual design of PhD training - forget about random internet forums.