Metallurgical engineer here. One thing I never see talked about on this topic is how astreoids don't have nearly the mechanisms for concentrating matals into ores like planetary bodies do.
So while there may be a higher proportion of, say, iridium on an asteroid than the average of Earth, it is pretty homogenous. You would have to refine the whole thing to get a little bit of iridium. On Earth, it may be more rare on average, but Earth also concentrates metals into ores via heat, gravity and water action so that you can mine a small area to get what your want economically.
Metal meteoroids are mostly iron, which is cheap on Earth and of little use in space. Aluminum, which is useful in space, is one of the most common elements on Earth and even higher on the Moon,, but it's only economically mined in tropical soil that had ages of water erosion. Titanium, different process but similar story.
Given the economics of getting to where you want to mine, mining a non-concentrated rock, and then transporting it back to Earth's for sale I just didn't see any path for mining asteroids.
Once there's is an established human presence in space, there might be a reason to mine organics (CHON) but that is not now and not what people think of when they tout asteroid mining.
There is a definite chicken and egg issue here. Until you've established a firm foothold in space, bringing resources back from space just isn't economical. Likewise, until we have a truly cheap way to get materials from earth into space, it just isn't worth it, either. Starship or similar will help, but there are long-term problems with using rockets to get stuff into (or back out of) space. But, once we have that foothold, there is a vast amount of resources on the moon and elsewhere that is pretty cheap to get into the neighborhood of earth. There are even ways to do this that don't use rockets, although we need to do more research to get these right.
Once we have that foothold, and either start colonizing space or make it even cheaper to access than starship hopes to achieve, a decades-long mining operation to free up highly valuable resources to ship back to earth while also freeing up large amounts of resources that would cost too much to ship from earth to build infrastructure in space, could become viable.
I wish I believed that would happen in my lifetime, but I hope it happens in my children's.
I think I'm saying that mining on asteroids will probably never be profitable or realistic (with a possible exception of carbon, hydrogen, oxygen, nitrogen CHON once people are living on orbit). Mining on other planets might require understanding different geology and maybe different refining technology. Anything mined on a planet will likely stay there. But there just won't be any ores on asteroids because they never had a chance to differentiate into higher and lower concentrations of various useful metals.