The user does hardly any config, really has no idea how it works, which could make diagnosing and troubleshooting issues that crop up problematic.
Not sure about the state of open source forum scripts, though I don't recall phpBB/SMF/MyBB being replaced by anything else in that market recently.
But personally, I'd recommend XenForo. It's what most of the sites I run use (see Wario Forums for an example), and it's what many sites I'm a member/volunteer on use too (like The Admin Zone or Gaming Latest). Lots of choices for themes and mods there, it's pretty fully featured as far as basic options are concerned and the media gallery/resource manager work well too.
The fact many members weren't too keen on the other solutions I suggested helped too.
But yeah, XenForo is my recommendation.
I've seen some enthusiasm around Discourse but for users who are used to the look & feel of a traditional discussion forum or the workflow of vBulletin, it can be very jarring. I believe there was a decent community split when Ubuntu tried to retire their legacy vBulletin forum in favor of Discourse; I think they are still running both side by side with almost different groups using them. XenForo is a more natural progression from vBulletin and would be my platform of choice.
https://www.talkyard.io/-32/how-hacker-news-can-be-improved-...
and looks & works a bit like Discourse, + also Slack chat features (no mobile app though) and StackOverflow style question-answers. Open source.