You seem to have a decent understanding of color theory, but your work is far from perfect.
You also seem to be getting too defensive right now to accept much criticism, but the people that are saying you need to work on your ability to create a strong silhouette are right. Silhouette doesn't just matter for Saturday morning cartoon characters. It is an integral part of the design of everything you see around you - from cars, to shoes, to lamps, to the trademarked iconic shape of the glass coca-cola bottle.
I suppose the thing that bugs me the most about both your 2d and 3d work is that they seem made up of a bunch of rounded shapes that don't have enough detail to be identified as anything. Your designs also seem to lack any sort of clear function. While I don't expect you to run of and get a PHD in mechanical design, you should either focus on making things look like they aren't just glued on randomly, or make things interesting enough to look at that no one will care.