Any forum seems to be a magnet for spam. Unless you get a spambot in there or hand out admin edit, delete to your forum managers you'll learn why in just a day why this is a big omission.

I looked again just a few minutes ago and PHPBB and didn't get the feeling it was not "modern."

If you want "modern" you may find yourself in a discussion like this.

Then again, maybe you just want the usual WordPress Forum? https://www.google.com/#q=forum+for+wordpress