What I hear from your conclusion is "screw anyone who isn't already in my network", and that sounds... sad?
Collaborations and discussions are always welcome and it’s not hard to get in touch with me, it’s generally very easy to separate this from the spam. Twitter is a better place than email to kick off a non-spammy relationship with someone you don’t know.
That said, half of the people who send this spam think they have a genuinely good reason and I have no doubt some of them even believe it. 99% of the time there isn’t a good reason, they are after something. “I saw you do after X and we provide Y which is necessary for X” is not a good reason. For instance, even if I’m hiring, unsolicited contact from recruiters who think they can fill that role is entirely unwelcome, etc.
I can count on one hand the number of fruitful outcomes from completely cold contact that I’ve experienced in >15 years.
I think this is a fair way to go about the problem of being unable to reply to a few million emails every single day, if you're really famous.
If someone isn't willing to put their money where their mouth is, then they can't have a genuinely good reason to reach out to me, I figure.
Ultimately, it really comes down to the intent.