You seem to be unclear on what "pixels" are, so I will try to explain. I apologize in advance if this seems in any way condescending.
The Nokia 3310 has a display consisting of a uniform grid of squares. The grid has 84 columns and 48 rows. At any given time, each square can be either a dark or a light color. It is not possible to have "half" of one of these squares illuminated; all graphics (including text!) must be drawn using these pixels as the minimum element of granularity.
Your game displays many objects at varying sizes which are not even multiples of a pixel size which divides your display into an 84x48 resolution. Objects move smoothly at "sub-pixel" intervals. Text is often scaled or animated in fine gradations which are not multiples of pixels and use anti-aliasing to smooth their edges. The background border of levels uses very finely-spaced lines which in practice appear as a different color from the proscribed 2-color palette. Even the introductory sequence of the game uses additional colors (black and white) beyond the palette constraints.
I hope this has helped clarify why your game has received criticism with respect to its adherence to the jam's aesthetic constraints.