That Focal should be fine as a center speaker, as long as it is vertical. It should be turned on its side.
I would check that your receiver has set the balance of the speakers correctly and check it with an Spl. meter if possible. Otherwise just try turning down the center speaker. Balance between mains a center is difficult to get right, but crucial. Center speakers are the most difficult to design, and most centers fall way short of the mark. You just need to experiment. I would not change all your speakers, but you might need a properly designed center. If it is a horizontal MTM, the that excludes it from the properly designed group.