Because politics is not limited to Left and Right, compressed down to it's minimum reasonable simplicity it is at least two dimensional. In mass media you see "Left" vs "Right" division, on Lemmy you see Lib Left vs Auth Right vs Center divisions, which are just as strong but largely suppressed by entrenched political interests especially in the US but also across the industrialized world where Lib Left has been suppressed by the capitalist political apparatus.
Note that most of the time when someone on the Fediverse decries "Liberals" they mean capitalist centrist in the "Neo-Liberal" mode. In some specific circumstances though you might see Auth Left criticizing Lib Left with the term, essentially insulting them by lumping them in with the Centrists. In other cases more in line with mass media you might see any Right position using the term against anyone center or left of center.
Essentially, Liberal has become a term only meaningful in context, and for that reason largely useless in common discourse. This is why the Political Compass is so useful a tool, situating political positions in their context, though of course it is flawed by being only two dimensional when actual political groups are very much multidimensional.