You gonna have a hard time getting a general consensus on this, people have a wide spectrum of experiences here, ranging from no sales to massive sales, this is common on all selling platforms bytheways.
The only thing you need to know is that this site has massive amounts of traffic (https://www.similarweb.com/website/cgtrader.com#overview) and there is great demand for 3D content. You only need to know what type of content is in demand and try to avoid making stuff that already is there in large quantity.
Dalia Lasaite, the CEO of CGTrader, presents the best practices for selling 3D models, the new Analytics tool for designers and trends in the 3D market (https://www.youtube.com/watch?v=xI_HpXuPWms). You definitely need to listen from minute 14 tot the end where she is talking about advantages of the analytics tool to get a notion of what is actually in demand.
I sell on average about 20 models per month here (with my small 53 models collection) and experience the website gaining ever more traction, my belief is that this website will eventually harbor all top professionals when they notice how efficient this site actually is (including the exclusives from elsewhere).
This is going to sound hard but if this site is not worth it for you then no site will. The potential is here but it remains to be seen if you can get it out. Do not blame CGtrader if you cant, it actually depends on you wherever you go. This place already has everything you need to make it, the rest depends on you.
These questions your asking here can potentially dilute yourself.
Are you motivating yourself to get actual results or are you measuring whether you should quit?
Tip: Just do what is necessary to get the success you want, ask the right questions, do stuff, fail and rethink until things work out.
This would be my advice to you and myself (because everyone forgets this from time to time).
The point is, no one can tell you upfront if you would succeed or not (this includes yourself), some (the less successful) will probably say its not worth trying, others (the successful) will probably say everything is going work out fine.
So you just going to keep getting conflicting messages.
Again, it actually depends on you in this situation, just make up your own mind and probably best not listen to the ones that not succeed and complain.
Are you going to do what it takes or not, that's the real question.
Quit if you do not like the work but keep at it if you love it and want it to lead to success.
Again, this place already has everything you need to make it work.