Well the only two sites I frequent that are based in Discourse are the Rocky Linux Foundation one - the spin after the CentOS had changed to CentOS Steam -
https://arstechnica.com/gadgets/2020/12/centos-shifts-from-red-hat-unbranded-to-red-hat-beta/ - that is a very small forum, and the Level1techs that looks like it is Discourse but can be something similar that is huge and with lots of technical info and activity.
My opinions are meh, I don't mind. It is true that "dinosaurs" like SMF, phpBB and vBulletin simply work and have a lot of development years plus a wide implementation on the WWW. But is also true that their layout is dated compared with the new trends, specially for mobile.
Discourse and other similar solutions - one proprietary that comes to my mind is reddit - are definitely more modern, nicely looking and support mobile and tablets natively or via an APP. Although the endless page load is very taxing on the memory of a PC. With 1 tab open on Firefox and 30 subreddits subscribed, some low traffic all day and others that have new messages each 10 sec in high traffic time, and uBlock extension working to not show the ADS, I can scroll until 1 day before (24 hours) and I start to note a slowdown on Firefox and 8GB of RAM consumed just on that tab.
Plus the internet points that most of this kind of solutions, a la Youtube, Facebook and Twitter Likes/Dislikes (that I despise, specially Facebook and Twitter that are mainly a Cesspool) that makes what is popular on top, most of the times as the laziest attempt possible, while good technical/informative posts are relegated to the bottom of the barrel because "they are boring" (the attention span of the new generation in full effect). For that reason I have reddit with the New option activated, that means that I see the posts chronologically by publish time and not by votes, like a normal forum is.
The reality is that both solutions fit their role, both have limitations. I think that it should be the kind of "don't change the winning team". Changing just for the fact of being "modern", "in", "trendy", etc means jack shit and will alienate a lot of current users, some who prefer the simplicity of how things are and others that simply don't want to learn a new way because how currently is works and don't need to be changed - and the human being is very reticent to change their way of doing things just for the sake of changing when both get the same end result.
Could look better, yes it could. But will it really matter when in reality we are here for the info and the exchange of knowledge, not for collecting badges or making a competition of who is the most popular. To me even the post count should be something that should be hidden or only count in certain technical subsections of the forum. I frequented back in the day a forum - the XtremeSystems Forums - that the counter was disable for threads created on the off-topic subsection that was the one with most traffic per day. Not only that but also because the Buy/Sell/Trade Section of the forum was blocked to users with less than 50 posts, so that way they kinda prevented the type of user who registers just to sell stuff.
But as also mentioned, all the info of the forum should be mirrored (and I'm sure that Dave done it already, mind it, this is not a critique to anyone, on the opposite) in case something very bad happens and all this info is lost. We already lost a lot of old discussions and tons of valuable info when Yahoo Groups closed and warn that all the info in the 18 years since they started was going to be purged, having the users to run against the time to archive years of valuable info.
I feel fine here, even if the "house" is not as modern as the other ones in the end of the road. The moderation and administration are spot on, not too much but also not too lenient. Even if sometimes the users are a little hard to talk with. Most of the times I'm afraid of commenting because there is people here with heck more knowledge about something than me but with bad temper, but as an IT guy is the same, no time for bullshit and stupid questions so I understand perfectly well. That makes me to really select what I can comment and will not get eaten alive by any stupid thing I must say. But enough, that is my 2 cents.