People blame Reddit, but it's not Reddit alone and this is extremely evident if you could see it for the demographics where nor Reddit nor English-based sites are the norm.
The main problem is the network effect (which Reddit did right) and what at 2010-2012 there was a massive change in the demographics of the new users on the Net: more and more people started to interact with it through the phones only. phpBB-like forums never had usable UI for the phones (though they are still a magnitude lighter and usable than modern Reddit, lol) and had one main problem: discoverability.
To Average Joe (who thinks Internet is that 'F' picture on the phone) the process of discovery (Internet search) and registration (e-mail based, captcha ridden) is way too much.
Add all other shortcoming listed in the other comments (notably the need to spend money, time and brain power on just maintaining the forum itself) and it's pretty evident why most of the forums died.
NB I still frequent one forum, site OP moved it to XenForo from phpBB years ago and did numerous modifications and integrations both for the old and new versions, which isn't available on Reddit at all.
Another forum is still running ikonboard, but it's userbase is... I'd say "not Discord/Reddit-compatible", which is also partly answers to your question: it is viable for some small (on Internet scale of things) community to thrive on a 'classic' forum software... but only if Discord/Reddit doesn't provide way less friction and/or discoverability.
The main problem is the network effect (which Reddit did right) and what at 2010-2012 there was a massive change in the demographics of the new users on the Net: more and more people started to interact with it through the phones only. phpBB-like forums never had usable UI for the phones (though they are still a magnitude lighter and usable than modern Reddit, lol) and had one main problem: discoverability.
To Average Joe (who thinks Internet is that 'F' picture on the phone) the process of discovery (Internet search) and registration (e-mail based, captcha ridden) is way too much.
Add all other shortcoming listed in the other comments (notably the need to spend money, time and brain power on just maintaining the forum itself) and it's pretty evident why most of the forums died.
NB I still frequent one forum, site OP moved it to XenForo from phpBB years ago and did numerous modifications and integrations both for the old and new versions, which isn't available on Reddit at all.
Another forum is still running ikonboard, but it's userbase is... I'd say "not Discord/Reddit-compatible", which is also partly answers to your question: it is viable for some small (on Internet scale of things) community to thrive on a 'classic' forum software... but only if Discord/Reddit doesn't provide way less friction and/or discoverability.