Have we already been visited by aliens?

It's not a homogenous demographic, and it doesn't have a substantial overlap. So there is a very large (super-majority) of medical doctors who have absolutely no training in research, statistics etc. Because it's not what they do - they are not scientists. Their training is about their obligations to follow current developments in best practice, drug prescriptions etc. (or the same but for surgical technique) and apply it. They do not do science, they don't even necessarily particularly understand the scientific method.

So it is absolutely incorrect to imply that all medical professionals are "the scientific community". They're not. Those which participate in and publish research are but that is not even a significant fraction of their population.

Comparisons about what general population surgeons and medical doctors historically reacted to changes in practice does not say anything about the idea that these people represent a peer-reviewed scientific consensus, because they didn't. They represent the equivalent of a mechanic rejecting manufacturer recommendations on fuel quality and complaining about it to their colleagues.

This isn't the problem I'm getting at. The problem I'm getting at is that it'd be highly unlikely for an intelligent lifeform (or really any) to develop under those extreme conditions. Advancing under other conditions and then developing towards extreme conditions after they have reached a sufficiently advanced state is a different issue.

For extreme conditions like operating at a speed much faster to us (imperceptible) would mean that they would be under high amounts of acceleration than compared to us. Gravity already puts major constraints on humans and for a lifeform to be operating at a rate imperceptible to us we're not talking about 10x or 100x the gravity but more like 10^10^10^10 (or more). Mind you that their internal reference frames (their internal clocks) would operate at a different speed than what we see their clock moving at. Subatomic particles have a difficult time operating at a fraction of that gravitational force. That means you have no building blocks.

What you're not considering is that I've accounted for things like chemical processes and electrical processes not being needed. The problem is that I don't know how you get two particles to change state (at least in non-extreme or destructive ways) under the conditions you're talking about. This isn't about "oh we just don't know" it is that there are some things we do know. We know that lifeforms have to be able to change their state (e.g. you can move your fingers or you can have a thought. These are state changes). We know the basic building blocks of the universe, quarks (or at best strings). There's certain rules these things have to abide by. You can let your imagination run wild but there are still limits of what you can do within this universe. And any being even visiting this universe would still be subject to these rules even if they were from a different universe that had a different set of rules. You can't just trash these rules in the spirit of imagination (which btw testing and updating these rules is what the job of a physicist or really any scientist is. But it is still a convergent process).

Creating things that last longer than an individual's lifetime isn't hard at all. We've done it by accident, they are called artifacts. Nature does it all the time, they are called fossils or just dirt. Trees last longer than human lifetimes. I know you think you're keeping an open mind but instead what you've done is limited it. Operating within the bounds of the rules doesn't have to be a limiting process. There may still be an infinite number of configurations under these rules. But abandoning them makes your search space so open (and open in a way where you wouldn't expect to find solutions) that you can never find what you're looking for. It is like if you're looking for needles in a haystack and arguing that the way to find the needle is to add more hay because the needle is inside the hay.