@yesco is right that practice is all over the place for IPv6 if it works at all. But in general, IPv6 as a protocol is just fine, at least equally secure as IPv4 and not more complex than IPv4 in many practical cases. I would even go so far to say it is way easier to do a clean address plan with IPv6. Usually, IPv6 inbound access is blocked by default on the ISP routers firewall.
In practical networks, IPv4 tends to be set up in some way and usually seems to work correctly - until you discover all the atrocious hacks people have commited over the ~ 25 years of practical, widespread use. Quite often multiple levels of NAT without much reason for it, UPnP where it shouldn't be, payment for even single IP addresses (great, we are paying for numbers other people got basically for free) and more - IPv4 are often handled like pets. Compared to IPv6, it is much harder to do a simple split into security groups based on prefix with IPv4. (In IPv6, you can usually just give every broadcast domain a /64 and will not do a huge mistake - they are a single security group. Sometimes, you might want to hand out a /64 or even shorter prefix to every client though.)
There are some great resources for modern and practical IPv6 too: https://knihy.nic.cz/#IPv6-2019 (4th edition in Czech by Pavel Satrapa, but can be translated using Google Translate and is more or less ok as a translation: https://docs.google.com/document/d/10CRjSRBLcdqtGjJgaW5Sct5h...) there are older books in English that are also mostly relevant still. The free IPv6 course by RIPE NCC is also a good way to get up to speed and avoid (spreading) FUD.