I was thinking about this just the other day, and probably the main barrier is everything needs to be created 'from scratch'. In LBP, you had characters with emotes you could drop into a creation (movie) and have them act, plus drop on costumes to give them personality, so creating simple stuff was easy. I haven't seen the same in Dreams, though of course you have premade items you'll be able to share and use. But that means that there's a whole load of work needed to create characters in Dreams.
It's traded work for quality. Far more quality and variety is possible, but with an increase in creator's effort to achieve that. My animation took some weeks, maybe a couple of months, in LBP. The same in Dreams would look a lot more professional but I can't see it taking less than many months to achieve a better quality result.
Well, the game will likely come with loads of characters you can either just drop in or tweak and (I'm sure) within days hundreds of others will be added. As for animation...I'm not sure what you mean (as I haven't seen your animation) - but I saw a demo where they literally record the animations by dragging the characters where you want them to go (not sure how LBP handled this) - it took seconds to do.
edit - have you seen this?