It is more likely that the creators with experience, good creators that have an eye for details, Creators that grew up with advanced tools, left poser for either Daz Studio or other platforms, allot also started making stuff for Industrially more advanced programs with a higher value for there works. The remains are rather unexperienced creators the main reason why most outfits are made as Dynamics, you can blame the end user if it does not work the way expected, you need allot more experience when making conforming stuff or standalone models.

Poser sure can offer great render results but here also, most that were capable are long gone. Poser is at a reset point causing that most renders seem like made at the time of posette, that goes all the way to the Product promo renders.

A capable creator will always choose the place where he can make most profit for he's work, it is a hard business considering that brokers charge 50%  a 20$ item must be sold 30 times just to get a day work covered, even then it is a cheap work, selling an item 30 times is now day's already " Top Vendor " " First Page " but consider that making a quality asset takes you more then a day of work .... 90% of creators end up with 50c an hour for there engagements.

Customers Have high expectations, They buy an 5-10$ asset and expect full lifetime support, updates, high end quality! Even if they get it for free they have expectations for support. 

Good experienced creators also get pushed off by users with attention disorders pretending having a great know how, shouting out loud, but in reality not even capable making a high quality render. Also a cause that quality creators look for a better place or a platform with better recognition for there work. 

For a Creator it is also Important having customers that are capable of using the software and produce good renders, This is Publicity, If customers, end users just make crappy renders then the creator will not get enough attention to sell the products and try to find a community with more creative potential to sell assets.

It will probably take decades for poser getting users back with a creative eye after the full reset and there is allot of concurrence at the moment, customers will always choose the place with the best visual influence and poser sure does not have a good visual position at the moment to get the deserved success.