Carrara needs a lot more or better features for modelling.  If you compare it overall to other apps, it holds up real well for the price, but if you really want something for more than rendering Poser stuff, then you find it is lacking in some really core features, like modelling tools.  Sure, you can model things in it, but it's not fun, and compared to something like Blender, it would take forever to model high poly objects in Carrara.  Carrara is cool, and can be fun, but for doing some real work, and creating scenes from scratch, with all your own models, it's kind of outdated.  Hey, that's just being honest.  I'm not trying to bash it, just being realistic.

I don't see many people creating really high quality models using only Carrara.  At least not on average that doesn't happen, and there's good reason for that.  Sure, some people probably do create some fantastic realistic models with it, but it's a rarity.  Hey, people actually still use Bryce for modelling some far out high detail models too, but it takes them months.

While there are some who use Carrara this way (Kixum and Mike Moir spring to mind) I don't generally think Carrara is considered by really anyone as the absolute GoTo solution for the 'awesome vertex modeler' category.  It's never been billed that way and I have serious doubt anyone ever bought Carrara solely as a modeler or with the expectation of getting Modo or C4D or 3ds level of modeling features.

But there is modeling and then there is modeling.  If my goal is that I need a precise complex model of something to machine tolerances and I need an app solely for modeling this one thing, which I can then convert into an .obj or something to be used in any other app, well then sure there are better apps for that purpose.

On the other hand, if you're in the middle of building a scene for rendering and you suddenly think, 'man I sure wish I had a wall over there with an doorway and some windows and some windowboxes with flowers, and some custom built trees' etc, then Carrara is perfect for this sort of thing without having to save the work, close down your app, start up another app, model from scratch, import into your original app, restart the scene you're work on, resize and rescale, and place, etc.  Eh, why slow down the workflow when it's as easy as slapping in a vertex object, hop into the modeling room for a sec, then back to the scene, ready to go?  The fact that this kind of thing can be done quickly and seamlessly in on app makes Carrara by default superior to any other modelling app (no matter how excellent the other modeler is in features that Carrara doesn't have) for quick and efficient workflow.

Also not to be underestimated is the breadth and number of Carrara modelers that are built in.  Leaving aside plugins like Architools for the quick construction of buildings and stuff like that, we have a ton of different modelers built in.  I think most people only think of the Vertex modeler, but there's the Spline modeler, and the Metaball modeler, modelers for Plants, Terrains, Clouds, Fire, Water, Particles, Text, Hair, to mention just a very few.  Are all of these different modelers the very best modelers of their type anywhere in the industry?  Of course not, but surprisingly some of them actually are (I'm thinking at the moment of the hair modeler which is simply outstanding for any hobbyist-priced software and fully the equivalent to what can be produced with pro-level priced apps).

But who buys Carrara just as a modeler?  No-one, except maybe Titanic401's fictitious and non-existent caricature of a Carrara fanboy strawman (which means no one).  The reasons for going with Carrara are multiple, but if I had to guess I would say it's ability to use Poser and Daz characters natively probably ranks high on the list.  The huge number of modelers is likely much lower on the list, and a side-benefit, for most (not all) Carrara users.

I would never ever argue with anyone that Carrara has the greatest and most feature intense vertex modeler on the planet.

By the same token, I think it would insanely difficult to argue that Carrara's multiple modeling abilities aren't incredibly useful within the context of a larger scene construction and workflow.

I know you mentioned it being easier to pose daz content in Poser or Studio (which I very much disagree with, but this is a subjective opinion only; for me Carrara is waaaay easier to pose characters with), and then exporting as .obj to render in other apps, I do this myself from Carrara, because I have a great love for TheaRender, and until such time as someone invents a plugin for Thea that's what I have to do.  But let's not pretend there isn't a lot of time and trouble involved in this process, it certainly isn't an efficient workflow, and nowadays if I need something rendered in an unbiased engine quickly and correctly, I use the Octane for Carrara plugin so I don't have to go to the trouble.  Sure Thea renders a bit faster than Octane, and I'm not as in love with Octane for it's rendering, but it's so close the differences between the 2 are negligable, and again with the plugin it's a one click solution within the same application.  That's a huge benefit to me in time savings, and I know I'm not alone in preferring the all in one solution in this way.  Again, not trying to bash whatever your favorite software or workflow is, just being honest.