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.
In addition to what you said, this season it seems that PSG will also be more overwhelmed to compete in the Champions League because the opponent that PSG will face in the last 16 is Liverpool. This is quite a tough challenge for PSG because the team immediately meets a very tough opponent in the last 16, while in Ligue 1 itself PSG can still compete more relaxed because the points gap that PSG has is quite a lot with all its rivals.