it is rare for a GK to get consistent high ratings of 7 or 8 and a rare 9

The fact is Nordeus has issues with rating GK the same as outfield players. They cant even differentiate them in terms of statistics. They dont have saves/penalties stopped/goals allowed etc....stats you would want to see before actually buying a GK.

All that to say: dont worry about ratings of 6-7 for a GK. 4-5 and you just sit him because he lost his "motivation" and is completely out of his stash of unicorn farts. Just send out invites for a bunga-bunga party and you will see his morale increase exponentially.