Looking at my piano playing, I find that the worst deficiencies are rather correctible.
*Mistakes. Well, just not playing as many wrong notes is doable.
*Legato. My playing is simply not legato enough. Even without the pedal, I could simply play more legato by trying to do so consciously. Even passages I think should be staccato sound better more legato than I am playing them, for example in the tune that I have nicknamed "Bouncy song." The sound I am actually going for is as legato as possible without the sustain pedal, if that makes any sense.
*Dynamic sensitivity. If I know the notes, then I can concentrate my efforts on playing with sensitive dynamics and legato phrasing. Mostly, I just over-emphasize certain notes that don't need to be played so loud. The piano is after all the piano-forte, so the dynamic range has come into play.
*Tempo. I don't actually mind the fact that I speed up and slow down at certain places. Some of that is implicit in the song itself. I just need to do that more mindfully and deliberately, so that ritardando and accelerando are not simply arbitrary.
Those four things will make my playing, if not exactly good, at least semi tolerable. What I want is for my playing to be a vehicle through which the song can be heard, without being an obvious distraction. In other words, I am a better song-writer than I am a pianist, but the main flaws are easily correctible. I'm sure that if I correct those four things, something else will spring into view to be improved, like clean articulation. I weep when I hear piano as it supposed to be played and compare it with what I can do.