Yeah, the level of gatekeeping is extraordinary. "Not only must you respect my political position, but your lack of nuanced technical information means you have literally no room to be part of the conversation!" I see similar attitudes about military matters, where not having served is viewed as a reason to completely dismiss concerns, rather than a valuable outside perspective to be considered.

I grew up in the gun culture, and we actually have a few guns locked up in a safe in my father-in law's garage, but I haven't been motivated at all to go get them in the last 5+ years, because WTF do I really need them for? I might grab the single-shot 12-gauge someday because casual skeet shooting is legitimately fun, but while I still have a sort of lingering "suburban white guy" interest, I just fell out of love with actually having guns over the years, and my fellow gun owners were a not insignificant part of that.

"Assault Rifle" is a bit of a boogeyman term, true, but part of the reason gun folks hate it so much is that while they don't personally intend to use their own toys that way (anytime soon), their favorite guns absolutely DO amount to semi-automatic versions of common military weapons. You know, the rifles one might need when assaulting an enemy position:

• lightweight
• compact compared to earlier weapons serving a similar use case
• accurate
• high rate of fire. One little factoid the gun folks don't like to have mentioned is that even the most common military rifles stopped being fully automatic years ago because it's wasteful, and most are semi-automatic and three-round burst (correction: The US Army retrofit its burst to have fully auto again, though the USMC did not). "They're not machine guns" is another way to weaponize pedantry. Semi-auto sends plenty of lead downrange.
• arbitrary magazine size limited only by material science and added weight
• quick and easy reloading of the rifle with pre-loaded magazines.
• easily adapted with aftermarket parts that enhance only anti-personnel activities (lasers, flashlights, bump stocks, bayonets, etc.).
• chambered in a mid-size round: high-velocity, small bullet. Designed specifically to do well taking down animals human sized and smaller, but lightweight enough to carry a shitload of them without being over-encumbered.

It's not hard at all to come up with an objective technical definition that has nothing to do with "scary looking or not". Find some numbers for the various criteria and make bright lines, such that weapons that are still legal will be more poorly suited to mass murder than the current crop of black rifles. There will absolutely be people pushing at the margins, but you can't let perfect be the enemy of good. But no... people like the feeling of power they get by having weapons that are virtually identical to the stuff that "warriors" have, so they're going to cling to them like their lives depend on it, even though statistically they very much do not.