Your art lacks of consistency and the good looking ones looks like traced drawings. Overall there is a lack of volume and no personality.
This one is like really bad. you're not 10 years old right?
I don't think that working on projects with other people is a good way to progress.
To be honest you're not good. You should take some art class and learn the basics first.
You're far away from being a 2d artist... so don't say that you're a 2d artist...
This isn't a useful response. This topic is asking for constructive criticism, hence the title. You didn't say anything constructive.
Personally, I don't think there's anything wrong with tracing something, especially when you begin. Doing so allows you to register useful patterns and techniques other people use to effectively express whatever they're trying to. The next step is to put your own spin on things, which is what you're doing. I usually only do pixel art or pen+paper drawing, so I don't have too much advice to give you.
One thing that did stand out to me is that some lines in your backgrounds look very pixelated; for instance the bed frame in the image below. I think the attempt is to make them look drawn, but I'd clean them up a little bit since to me the effect looks a little too overdone, to the point where the bed frame looks a little bit like it was resized.
Another thing I noticed is that you're using the same saturation and value (someone correct me if these are the wrong parameters, I still need to study color theory) for the characters and the background. Usually you want to use brighter more saturated colours to draw the eye of the view towards important details. In your case I would think this would be the characters. Although, you are managing to accomplish this eye-grabbing thing somewhat with the thickness of the lines.