So you can get the scoop straight from the people directly involved.
While I think the reasoning for this decision is very sound, the unfortunate fact remains that since Linden Lab is a smaller company with limited resources, feature development will tend to lag behind off-the-shelf engines like Unity and Unreal, which have bigger development teams and lots of users. However, as mentioned in Inara’s notes, backwards compatibility of user-generated content (UGC) is a key issue that needs to be addressed in any successful virtual world. I still think that Sansar is on the right track.
The 20-minute video is a joy to watch as BigEyed Kitteh encounters various people in Sansar, and tries on various outfits from the Sansar Store. She seems particularly mesmerized by an animated NPC deejay with some seriously strange movements! Definitely worth a watch.