If PSG players and coaches are convinced that winning Ligue 1 is very easy then they don't need to try hard, I don't think they would be able to win Ligue 1. As a fan, I celebrate winning the title because I know that for PSG to win, it is because they invest a lot of money by hiring good players and a good coach.
If other teams also want to win Ligue 1, they should make good investments. This season's PSG doesn't have players with a great reputation like Mbappe, but they still won Ligue 1. Now, about the European Champions League, that's very complex. In the European Champions League, there are many good teams that also make good investments, so it's not easy to win and PSG shouldn't spend a lot of money just because they want to win the Champions League.
No matter how great a team is, if they do not play with their 100%, then they are not going to win a title. Look at Manchester City this season, they are fifth and doing badly, they just got a draw against Manchester United who is 13th.
City won the league four times in a row, and at the start of the season most of the players were the same, sure they added some new players during winter break, but most of the players were the same at the start, the team that won premier league, a much more competitive league, four times in a row, six times out of last seven, ended up being fifth right now. Because they didn't play with their 100%, that is why they lost. Same with Bayern Munich last season as well. PSG needs to keep playing with their 100%, or at least 80-90% to make sure they can win it.