There are no secular Jews. All Jews are holy, because when the Torah was given at Mount Sinai, all Jews became members of a holy nation.
True, they have free choice to decide what they want to do, to say, and to think. But they can’t change who they are, and they are all members of a holy people. Holiness is the polar opposite of secular.

Why can't they change? Are you saying that they are hopelessly stuck, chas v'shalom?
I was one of those misguided Jews for 61 years. I thank HaShem that I changed four years ago!
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What term should we use when referring to Jews who dress and behave immodestly; do not honor or keep Shabbat and Yomim Tovim; reject what they know of Torah as being full of old stories/myths and outmoded laws; etc? Who flaunt their assimilation and don't know or care what a psalm is? And yet many of them shout to the world that they are Jewish and confuse the nations? Chas v'shalom!
Besides the words "sad," "pitiful," "willfully ignorant," "disrespectful," etc.
Their souls may be Jewish, but they clothe them (with thoughts, words, deeds, as well as literal clothing) in garments of unholiness and disgrace.
"Secular" seems a polite term.
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I think we should spend more effort trying to wake them up, rather than excuse them.
May HaShem Yirachem guide us, and reveal Mashiach NOW!
True, we tend to see those things that are most visible, most important to us, and distinguish us from them. So we say we are observant and they are not.
But a tzadik sees the essence of each thing and of every person, the point at which we are all one. He sees the soul and it is a holy soul.
We believe in ourselves and divide ourselves apart. The tzadik believes in us and pulls us together.