QGIS will, for raster basemaps, fetch the detailed version to get you your high DPI detail but this of course involves stitching together lots of tiles from the basemap's lower zoom levels - which then have small labels. For raster maps which are not labelled, it makes complete sense and produces a much better result than the alternative (picking the "scale based" zoom level and interpolating).

This is kind of the only "right" answer when dealing with raster basemaps. It's either pixellated or going to be rendered "too small" for the zoom level.

Vector basemaps don't have this problem, and QGIS supports them, so that's the way to go if you can get data. QGIS can then render at the required DPI in full clarity but with elements scaled/positioned appropriately.