a score of 5 for this tired old ignorant shit? Alright, let's get cracking.
RA, aka. ICMP router advertisement. Abandoned circa 1970 as a "bad idea". It was a colossally bad idea in the 90's, and f'ing suicidally bad in 2000+. Yeah, let's trust whoever the f*** on the cable claims to be a router and send it our traffic. Oh, to protect my network(s) from that brain damage, I have to buy new switches that support "RA Guard"
Right, because DHCP totally solves spoofing problems yeah?
They didn't like DHCP. So "no f***ing DHCP in IPv6!" DHCPv6 is a bolt-on, staple-on, and bandaid addition to IPv6. It's a horribly incomplete shadow of DHCPv4, and still requires an RA tell you to use it.
No it isn't. You can do practically everything that DHCPv4 does with DHCPv6. Yes you should send an RA, so what? DHCPv4 is as much if not more of a bolt-on than DHCPv6 is (in so far as it's absolutely not part of the protocol stack whatsoever)
SLAAC... originally 80bit prefix plus 48bit MAC. They ignored the fact that ethernet is not the only technology in the universe. That was later amended (breaking older stacks) to 64bits. The entire purpose for the vast over-simplification of address selection (for tiny embeded systems with limit RAM/ROM/CPU) became moot 7sec into the IPng committee's existance -- IPSec shoots all three in the head, repeatedly, with artillery. Everything supports privacy extensions these days, so the logic for random address generation and duplicate address detection is there -- and rather trivial. Yet it, and SLAAC, demands the prefix-length be 64. Just to put that silliness in perspective, that's a single LAN with every ethernet device ever created (that will ever be created) in it 65,536 times over.
Just to put YOUR silliness in perspective: the remaining number of bits is 2^61 (within 2000::/3 obviously) which comes to 2,305,843,009,213,693,952 /64s. Get a damn sense of perspective. As far as "older stacks" go... clearly not anything seriously used in production today.
This leads nicely into the blindness to history... a 64bit LAN is pure lunacy. Today and likely for several decades. But we "have an infinite amount of address space." Actually, NO, it is, in fact, quite finite: 128bits, to be exact. If we carve it up with the same pez-like abandon as the early IPv4 assignments, it will be even less "infinite". Sure, we can change the way we do things "with the next ::/8", but that dooms us to live with the colossal stupid of this ::/8 for ever. Again, dooming us (and our children's great grand-children) to live with our bullshit. We did a lot of stupid things with IPv4; and we're doing them all over again with IPv6.
No, your failure to grasp the scale of numbers is pure lunacy. If we somehow manage to fuck up 2000::/3, there's several times the size of the current global IP space waiting to be spun up with the flick of a pen, so we have plenty of opportunity to make mistakes.