There was that MP game where i sat in my awesome Korea after taking those 2 provinces that Korea has unique missions for +Girin, not really doing external expanding after that. People laughed at me, carving wide steppe empires, getting new neighbours and new enemies, while noone dared to attack my border forts with +3 attrition bonus, with a decent amount of combat-ready troops standing near my borders... They laughed, they were sure that i am not an issue. Even after i became a Merchant Republic and started dominating the Beijing node. Yet noone was pleased to discover that i am actually strong, with 400k-strong army and about 700-ship fleet in 1700. They died in great quantities in my mountain border forts with that extra Korean punch. I stayed on the defensive and threw them back time after time, again and again. Then i went on a counter-offensive. Result - i blitzed 2 of my enemies, peacing out for the whole of Manchuria, from which i released Yeren, fed it all the conquered provinces and made it my march. Needless to say, when the game finished at 1820, that march also was over 1k dev!
I know this is far from being optimal and that i did not win, only being a rank-8 great power in the end... But what a blast this game was! So definitely yes, developing may be fun for a change and can be surprisingly effective if you stack related bonuses.