Except that IPv6 is actually not that large. You effectively can't use networks that are smaller than /64, because stateless autoconfiguration can't use any other prefix size (there's an effort to fix it, but it'll take a decade at best)
If you rent a vps with a ipv6 “address” you will see that you are given a /64 network.
There is no effort to “fix” the bottom 64 bits because it’s not needed. There are enough /56 networks to for the next 500 years and 99% of people can do everything they need with an isp provided /56. IPv4 has survived with 48 bit nat for this long so 64 bit is even more buffer space
Unfortunately, I've seen multiple VPS providers that will assign you a single address within a /120 or something ridiculous like that.
I presume whoever runs the network side of things with those VPS providers has never used IPv6 themselves or they must be _extremely_ stingy.
SLAAC works on any device that supports DHCPv6, though, so you might as well use it if you don't have any requirements to favour DHCPv6