Sure, but if they're a new ISP, chances are they have a hard time getting IPv4 and they likely run CGNAT. If they run CGNAT, the benefit of IPv6 is there's a lot of high volume traffic that will move to v6 and the CGNAT use will be smaller. Routing v6 packets is much easier than tracking connection states and munging packets...

If they have enough v4 for all their customers, sure fine.

On IPv4 with CGNAT you get blocked and sent millions of captchas because you are sharing an IP with 5 IoT devices actively running a botnet.

On v6 you don’t have that problem.

Well, one benefit is that your users will not get blocked on websites because someone else with the same IPv4 did something suspicious.