Using forums on a VLE is a great way of providing a place for text based discussions. The asynchronous communication medium offers a very different experience to a face to face discussion in a classroom situation; one that some learners may prefer. I have never thought that online discussion forums replace classroom discussions, no much more they complement what happens in the classroom. Different learners will prefer different discussions, some will enjoy the spontaneity and immediacy of a face to face discussion, others will prefer the reflective thoughtful aspect of a text based asynchronous discussion. Similarly the context may affect the choice by learners, they may prefer face to face for certain topics and textual for others.
It can be easy to focus on text when using online discussions, but it is very easy to use images (even video) in a forum to create a visual discussion.
Images can be used as the stimulus for a discussion or learners can use images for their responses. In a similar manner you could use video.
Video and images can be really useful for those learner for whom writing is a challenge and can make what was a text based discussion an accessible discussion.
Adding images and videos to a text based discussion on the VLE is one way that you can engage learners to make use of one of the more useful and interactive features of the VLE.