The old forum was just a forum without social network functios. There were no modern user profiles, no responsive display, no download center, no videos possible, no picture upload, et cetera. I can't see that the old forum was better in any way... Regarding the "usability" I just can say that it is maybe a subjective thing. What makes it better from your point of view?
I for myself enjoy big font-sizes and a clear layout. And I already said that the categories will come.
Classic phpBB forums (and similar products) are also responsive nowadays and have modern looking templates. You can upload images as well (I don't know about embedding videos). Speaking of usability, I miss (for example):
- subforums for different topics (okay, categories seem to be on their way)
- possibility to jump directly to the latest post of a thread
- see my unread posts (and possibility to jump there)
- see in which threads I have posted
- preview a post before submitting (even if you have a WYSIWYG editor)
- display the name of the user who has been quoted
Small things maybe, but they have become standard features through the years, because they turned out to work well and enhanced the usability. Or as AFRLme put it: existing forums usually already have all the features you will ever need.
By the way: the responsiveness of the current website is limited. There is a phone resolution and one for big screens. It doesn't work well in-between (using FF).
After all, I have to admit, that I haven't visited the Visionaire site often lately. So you might better not consider me part of the main target audience.
And before sounding too negative here: the website looks much better than before. Better structured and clear!