That's what makes Doctor Who so special in the first place; adherence to coherence is never the show's (or any popular franchises) forte and I believe the showrunners understand it too as long as they tell a compelling story to compensate for lack of continuity. In-universe, changes in canon can be either a result of the Doctor repeatedly changing the timelines even without both knowing the whole picture while risking the destruction of space and time continuum, the perception of different characters from their own lens Rashomon-style or like the Doctor himself, the show just simply 'lies' at you in a cryptic meta way.