Has the CFP made it easier or harder to win a national championship?

Argument 1: It's easier.

During the BCS era, outside of when LSU won it all in '07, you needed a near perfect season just to get into the NC. You could actually go undefeated, win your Power 5 (then BCS) conference, and still get left out of the game. I'm sure Auburn fans are still pissed about that '04 team. And if you weren't Alabama, like UGA in '07, you would get penalized for not winning your conference (LSU jumped UGA that year to get into the NC game because they were SEC Champs). Alabama obviously doesn't even need to win their division to get into the game regardless of the system, but every other team had to win their conference to get in during the BCS era.
In the CFP era, there have been multiple teams that have not even won their division that have gotten into the playoff. All of this evidence points to the fact that the CFP makes it easier.

Argument 2: It's harder.
I'm convinced that more often than not, especially when the SEC went on its dominant run of consecutive national championships, one of the teams in the BCS championship game didn't really deserve to be there. The two best teams often didn't play each other. This was most evident when Alabama absolutely destroyed Notre Dame in 2012-13. Many believed that the real national championship that year was played in Atlanta when Bama took on UGA. During the latter years of the BCS era, it was actually harder to win the SEC than it was to win the national championship.

The CFP basically ensures that you will have to play and beat the real second best team in the country to win a national championship. And it means more tough games against really tough opponents that require you to potentially travel across country on short rest.

Ultimately, my opinion is that the CFP makes it harder for every team not named Bama because you actually determine who the best team is on the field. It's not a "mythical" national championship.