You lost your imaging the minute you put the speakers right up against the wall. Only thing worse you could do is put them on an actual bookshelf with books and stuff lined up flush with the front of the speakers.Books can actually disperse the reflection and act beneficial
This is because all speakers, in order to sound their best, need to be set up so the sound goes from the speaker to your ears. What you have now is the sound goes from the speaker to the wall to your ears. Every sound coming off the speaker reflects within a millisecond off the wall, and not just the once either but constantly across the whole surface of the wall, until the sound reaching your ears is this garbled mess, which is why they image so poorly now.To which wall? By placing them theoretically flush with the wall, you actually remove reflection from back wall and you get an infinite baffle that can reinforce lower end. That way you could get by with compression box which will have better transient response and still get good bass extension. Then, there won't be any baffle step that needs to be taken care of in the crossover at the expense of loosing efficiency.
If the wall is treated/covered with absorbing material I don't see any problem with imaging. Imaging is is defined by cues higher in frequency where the speakers are directional anyway.
There are speaker designs for wall mounting or against the wall and they can work pretty well.