If you realize it, PSG are way ahead even when PSG were still part of the UCL. The only thing that needs to be underlined is, PSG are still not strong enough because even though they are good in Ligue 1 but they are still very weak on the European stage in the UCL of course. So, I personally don't say Ligue 1 is boring because PSG dominate, because PSG can still be held to a draw and also beaten by mediocre teams moreover PSG have a star squad but they can't promise consistent wins and that is something weak.
I do not think that French league is a bad one neither, but when one team is as rich as PSG, it makes the other teams look not so great, plus that results with them ending with winning the league over and over again because they spent so much money, which makes the games boring, which makes the whole league boring after a while.
This results with less people watching because everyone knows PSG will win, and causes the teams to earn less from TV rights and merchandise, all coming down to league getting worse because of it. A league (or even nation) needs to have a football culture where even the small town clubs should get fans, that's how England got better.