The complaint is about the table
Almost every dismissal of French football reduces to the same observation: you can usually guess the champion. That is a fair description of recent history and a poor description of the league, because it treats one position in a table as the only thing worth assessing. Nobody watches a Sunday afternoon fixture between two mid-table sides to find out who wins the title, and those fixtures are where most of a season actually happens.
Leagues with genuinely open title races have their own version of the problem, where the bottom half is a procession and the interesting football is confined to six clubs. Every division concentrates quality somewhere; picking the concentration you dislike and calling the rest a farmers' league is a preference dressed as analysis.
What is actually there to watch
The French league is physical in a way that surprises people who arrive expecting something technical and slow. Duels are contested, transitions are fast because teams commit players forward, and the refereeing tolerates more contact than in some neighbouring leagues, which produces matches that are ragged and entertaining rather than controlled. If you like football that looks slightly out of control, it is one of the better places to look.
It is also the league where you see players before the rest of the world does. That has a value beyond scouting curiosity: watching a nineteen-year-old learn the position in real time, mistakes included, is a different pleasure from watching a finished player execute.