Don't forget DQIX was originally targeted 2007 release. it was pushed to 2008, than March 2009, finally July 2009. Also keep in mind how late DQVII came out during PSX life cycle. It came out after PS2 launch. DQX was confirmed in 2008, yet people only learned it's a MMO in 2011. It came on fucking Wii in 2012 which was pretty much dead at that point. Let's not pretend Enix side is much better than Square when it comes to scheduling.
But I admit, you have some better examples than XI there. I guess Square has gotten worse and Enix better? They release a lot of DQ games other than the mainline ones too.