Fortunately, as I grew older, there came a turning point.
你的句子 come 仍是不及物动词，这可以看作倒装句，你也可以比较 there be句式（比较：there was a turning point）。
There came a decided drop in prices. 物价出现了明显的下降。
There came a knock at the door. 传来了敲门的声音。
There came a sudden rush of water out of the hole. 从洞里猛地冒出一股水来。
There came a ripple of laughter from the crowd at the speaker’s little joke. 听到演讲者的小笑话时，人群中传出轻轻一阵笑声。
There came an explosion, not so much a bang as a shaking like an earthquake. 发生了一次爆炸，没听到一声轰然巨响，倒像是地震那样地面猛晃了晃。