peanut-walrus parent
Personally I find just using nftables.conf straightforward enough that I don't really understand the need for anything additional. With iptables, it was painful, but iptables has been deprecated for a while now.
Same here, I'm surprised most linux users I know like to install firewalld, UFW, or some other overlaying firewall rather than just editing the nftables config directly. It's not very difficult, although I've never really dug deep into the weeds of iptables. I suspect many people who have used iptables long ago in the past assume nftables is samilar and avoid interacting with it directly out of habit.
With nftables you need to learn a lot before you cam be partially sure of wbat you do.
With ufw gui you need a single checkbox - block incoming connections.
Not sure what you find difficult about it, but I just took the "workstation" config from the gentoo wiki and used it on my laptop.
Perhaps if you're doing more complicated things like bridging interfaces or rerouting traffic it would be more difficult to use than the alternatives, but for a simple whitelist it's extremely easy to configure and modify.