We've all experienced the infamous "OOPS, something has gone wrong ...." message. Over the last season or two it seems to be happening more often and while doing more things on the site. Some time ago we were told this occurs when the server is under heavy load, so effectively a time out problem. Also training is now regularly running late, people complaining about long gaps in next cup games being generated, delays in purchased players joining teams, etc.
While an app may bring in more users, or at least help retain existing ones, surely getting the existing infrastructure upgraded to improve the user experience is of higher importance. Otherwise if you bring on more users, once they experience the above issue you will likely lose them, also the added load of the new users will likely increase the occurrence of these problems further frustrating existing users.