New door installed is uneven after trimming at the bottom. Is this fixable?

If you mean the gap all the way along the bottom of the door is not equal from the hinge side to the other it is because it would have been cut to accommodate the floor level on opening, how big is the gap on the opening side when he door is fully open? Should just be enough to clear the floor covering.

If the gap remains the same at all points during the door opening to its full extent then the door can be taken off and a new piece of wood planted onto the bottom which then can be shaped to fill the gap. If the gap changes the this means the floor is uneven and this type of repair might not be suitable. If a plant repair is suitable and the door is painted then the new wood can be repainted to match existing to form an invisible repair. If is is a solid wood finish it can be difficult to match the colour and if it is a veneer finish then it is even more difficult to make this repair look neat. One quick fix can be to fit a brush type draft excluder. These can be fixed in such a way to even up the gap at the bottom so it does not look so badly fitted.

Hi. Do you mean the door is shorter at the top? The side of the door that closes to the frame, and the gap is where the frame doorstop is?