Patents are regularly invalidated due to prior art. As long as you document your inventions thoroughly, then even if you don't patent the idea yourself, you can invalidate the person who did. If the people who "call dibs" are being rewarded, it's only because the inventors either weren't patenting, or weren't documenting.
You know what's required for a patent to be awarded? It has to be non-obvious. It has to be something that someone "the typical person in the field" wouldn't think to do, when given that problem to solve.
If the patent office (and later, the courts) would just apply the non-obviousness criteria reasonably we wouldn't have these problems.
And yes, that means they'd likely need to consult with people in various fields. It's not exactly free to get a patent; some of that money could go to pay those same consultants to judge the obviousness of each patent as it is reviewed.
Agreed, but given that inventors can endlessly refile with whatever minor tweaks they like, and examiners are incentivised according to the number of patents they grant, it isn't hard to wear them down, eventually.
Courts then presume a patent is valid and it takes a lot of effort to convince them otherwise, and typically it is only prior art that will do it.
This is completely wrong; their incentive is actually to reject an application. The optimal strategy for an examiner seems to be to reject an application at least twice, usually more. There is abundant literature on this topic, and I encourage you to explore it.