Why prefer it over CharacterBody2D? Thought it works fine
Well, that is intended. Removing acceleration and adding instant max speed would be a couple lines of code change, but it would decrease purpose of other mechanics like friction. Gameplay is designed in a way to utilize player momentum so you have to plan your future moves in advance. I might consider increasing acceleration, but removing it completely is a bad call imo. The character instantly achieving max speed starting from 0 speed looks stiff and unnatural to me.