Mercator is conformal. Angles are accurate, that's all. It provides accurate navigation, which is great if you are planning a boat trip with middle-ages technology, but not fit for any other purpose.
That was kinda my point; unqualified "accuracy" is not an useful metric for evaluating map projections, as most of them are accurate in one way or another (and inaccurate in other ways).
Arguably the "best" (general purpose) projections are the least "accurate" ones because they use a compromises between different projections to make a visually appealing map.
Despite its shortcomings I'd argue that Mercator projection maps (in general) are accurate.