The only things I would ever modernize about the D forums if I were to ever bother is just CSS style or something, but honestly, they work, they're faster than most forums out there and aren't crashing all the time (I'm looking at you vBulletin!) so it's fantastic.
Vladimir Panteleev did, though, write a web interface to NNTP:
https://forum.dlang.org/
which is also freely available:
https://github.com/CyberShadow/DFeed