Your OP intrigues me because the framing suggests it's a stretch to believe in a forever-earthly-paradise. It's not. In fact, in the JWs growth heyday,this was the very carrot that drew so very many to the feast.
I suggest it is far less difficult coming to believe in a more perfect picture of what you already have (life on earth) than to embrace the airy-fairy way-out stories of life in another realm unlike anything on earth taught by so many other churches.
I've got nothing against angels and celestial choirs - and Ezekiel's visions have a certain captivating quality - but for many humans, a better earth is more imaginable from a religious perspective than an eternity above the clouds.
But as others have noted, Adventists and Christadelphians were the first to pine for this more perfect paradaisical earthly tomorrow.