While it's true that the Rams are changing their starting center I don't see why that means they should have drafted one. For all any of us know Allen and Corbett are both better than any of the guys they could have drafted. The most we can assume right now is that Allen is better than Corbett. I'm not sure how anyone can say that any of those rookies are better than Allen. (And we won't have any real data on that for months.)
DJax is on a 1 year contract and also has a recent injury history. The Rams have been quite proactive in drafting guys a year before they will need them and this seems to fit the mold. Tutu can get this offeason under his belt, learn from DJax, potentially provide that deep threat this year if DJax misses time, perhaps even gives us something returning kicks and/or punts or even a few special Tutu plays on offense, and then gets another offseason to prepare for taking over DJax's role in 2022.
AlbaNY_Ram