Positional plans can fail tactically even though their concept is very good. If they improved their tactical awareness and still sticking to their fundamental plans, they would be even more effective players. They would not Fall for silly tactical traps set by their opponent. Beat around the bush excessively with positional play- when there is a clean kill tactically they can play that instead. It is not enough to judge positions based on how good they look, and superficial judgements.
Tactical variations provide reassuring evidence for one side being better or worse.
The practical problems associated with implementing a plan are emphasised in the form of tactical variations. This may radically effect the choice of plan altogether in some cases. The positional player protagonist could argue that they play positional openings and stay well clear of tactical complications. The positional player needs to be tactically aware even if they do build their own infrastructure in terms of openings for example, for supporting their playing style. A chess player should learn tactics before positional play, because winning will usually be as a result of tactics not positional play.