PSG have single-handedly won the France League title in the last few seasons, and in each season PSG have had more points than the second-placed team in the table. PSG can win the title in this league as easily as no other league team can win the title so easily. If PSG were a Premier League or La Liga team it would be fine because PSG would have their equals there. If a good team regularly competes against weaker teams, then at some point that strong team becomes a weak team because that strong team has no idea about the big teams. That's the case with PSG at the moment, they play the entire season against relatively weak teams but when they come up against strong opponents in Champions League matches, they don't perform well there
I think the reason why PSG can't compete fiercely in the Champion League competition is because League 1 is not competitive even in the last few seasons no team has put pressure on PSG to defend its title and it's all because of PSG's financial strength which is above average of other teams.
And I'm even sure that for the next few seasons it will be difficult for other teams to compete with PSG unless the team management is willing to spend more money to buy quality players in all lines.