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.