
Tillich's "ambiguity" was very approachable in my youth, but today I find it extremely dangerous from a moral and philosophical perspective. There is truth in what is said, but unless you have the context in which it is said you can quickly spin it to your heart's delight. My primary takeaway as a youth was "this is great and very theological/intellectually stimulating while not morally demanding of me whatsoever, hooray!" which is why, as a stubborn young adult, certainly found it attractive.
FWIW, if anybody wants a great challenge that seeks to bridge classical theology with modern/personalist/subjective thought, you should read Man and Woman He Created Them by John Paul II. It is as rewarding as it is dense and gave me the bridge between "old" and "new" philosophy/theology that I find lacking in many moderns.