I can't use vlans because my isp only gives me a /64.

So I either need to use ipv6 + kludges or ipv4 + kludges. ipv4 is obviously easier and more reliable at that point, it's a no brainer.

Any sort of hot spot / bridge faces the same problem.

Now RFC 9663 is supposed to help here but guess what? It's only like a year old and barely exists. Not 20 years.

It's not that change is painful, it's the ipv6's original design of a shallow depth network was just... bad. Bolting on RFCs to fix it is taking a long time.