There are several problems with your argument.

1. How do you distinguish legitimate and illegitimate patents. I guess you have to agree on some arbiter, like courts of law. So that's how we are in the current situation

2. Notwithstanding the issue around deciding between them, most larger patent holders have a huge portfolio of "clearly" legitimate and illegitimate patents, and they are using both (you don't need to sue to use the patent, just threats are enough)

3. If you ever spoken to a patent lawyer, the whole process is about making the patent as broad as possible without disclosing how to actually do it (at least if you are using the technology yourself). So one might argue it's about making the patent as illegitimate as possible, because then the patents are actually useful (otherwise they are just to easily worked around) .

Patents need to be discriminated based on some threshold of originality or something similar. My country even has a term for it "verkshöjd" that is applied in this context. That way you don't get trolls trying to sue Amazon for "Way to sell merchandise using a >>computer network>>."

Of course there's no easy way to distinguish _all_ patent (applications) this way but that one would not be accepted.

The issues you raise are certainly valid and reasonable but notwithstanding not the point of contention here. The trolling part is the one that comes from what is perceived as illegitimate claims/ patents.

I believe most of the time 1 and 3 applies to the same company (if it is big enough) simultaneously because companies want to be one move ahead of their competitors.