If the person in question has never had the need to know iptables, why would that change now? If a job will require such knowledge, they will pick it up. Iptables is exposed as a facade to nftables, lots of the concepts just transfer over, just that iptables is the more antiquated option.

I for instance have never really used iptables in anger, but have lots of experience with nftables and pf. I’ve used both in a professional setting. People can be made aware of iptables, but unless there’s a need to know it, I wouldn’t recommend picking it up now. And you’ll know if you need to learn c++17 or iptables, or python 2.7.