I don't remember 6 or 7 center fielders going down due to injury. The Twins may have rotated that many players through the position, which I would wager is very close to the average number of CFs a team fields over the course of a typical year. The point isn't the total number, it's the level of talent in the number.
I'm surprised you raised the point of the CF depth instead of pitching. Anticipating that type of response coming down the pipeline from you or someone else, most teams put over 30 pitchers on the field over the course of a season. The 2021 Twins have used 35, the 2019 Twins used 31. I'm doubting that those 4 extra pitchers are responsible for 30-40 more losses. I'm betting you have the same doubt.
So yes, injuries are a factor. The Twins knew this but did not adequately plan for it. Choosing CF as your example is even more strange, given the Twins know the name on the back of the jersey for their starting center fielder and know he is often injured.