I understand the reasoning behind this. Official forums are difficult to maintain and moderate. Bioware would not be the first gaming company to offload their forum to 3rd party sites. I still sometimes find links to D&D build guides that point to the (now shuttered) official forums for D&D.
That said, I'm
very bummed out. The Tumblr and Reddit DA communities are very positive and nice, but the rapid time-decay of the discussions makes it impossible to have in-depth lore, character, or build guide discussions.
On a more human level, I'd miss interacting with the specific people who are on this forum. Seeing Sylvius' posts, never sure if I would agree 100% or disagree 100%. Riffing off each other on the Twitter thread. Casually chatting about favored abilities or teams on the combat forum. Sneaking puns about butts into Solas speculation threads. Hell, speculation in general - the frenzied lead-up to Inquisition was damn fun, in its own weird way. Not to mention speculation about the new secret IP, which probably contains shark-riding vampires in bikinis, based on our expert sleuthing.

The forums have a reputation for toxicity, but this is kind of overblown, IMO. Blocking is easy, and the rest of us have had really in-depth and mature discussions about the themes of the games. Even when those themes touched real-world topics, the vast majority of the people here are able to talk about them at length, really unpack them, without flinging feces at each other. I can't find that level of discussion on /r/dragonage, for example, because posts fall over time and people don't have a strong sense of their own identity. User accounts don't matter on Reddit - I can create 5 different throwaways to represent 5 different facets of myself. On here, I'm Arvaarad, and it's more challenging to spawn new accounts willy-nilly.
That makes me more aware of the identity I want to cultivate. When I'm making a post, content quality/friendliness is important to me, in a way that's less present on other communities. Based on the posting quality here (ignoring the trolls, which again, are easily blockable), I think that motivates many of the others here too.
If it's feasible, I would be very happy to see Bioware reconsider.