The answer is yes, and no, and it depends, and we don’t really know.
Yes, the simple essence is perhaps more or less timeless and universal. It’s all the divine. And the divine, locally as us, can discover that – and live now from it – through sincerity and basic practices and pointers.
No, a lot in spirituality (and especially religion) is not timeless. Religions come and go. Spiritual taurine come and go. Specific practices come and go. The specific context all of it is understood within comes and goes.
It depends on what we are taking about. As said before, some of the basics – in terms of understanding, practices, and pointer – seem more universal and timeless. And a lot is more specific to a time, culture, and tradition.
And more honestly, we don’t know any of this for certain. Even what seems more timeless and universal can and will change. It changes with the time we are in, our culture, and our general worldviews and understanding of really.
Is it likely that spirituality, and even more so religions, will be quite different in a distant future? Yes. Is it likely that if there is life other places in the universe, and interested in these things, they will have a different take on this? Yes. And is it still likely that the essence may be somewhat similar? I would say yes to that too.
What do I see as relatively timeless and universal?
The main is that all is the divine. Existence – including us and all our experience – is the divine exploring, expressing, and experiencing itself.
Spirituality, at least the typical human version, is about helping the divine – locally as us – rediscover this and live more from this in daily life. This too is part of Lila, the play of the divine.
And what about spiritual practices? These are a little more tied to a time, place, and tradition, but there are perhaps some universals here too.
Guidelines for our life. (For social and community reasons, but also to minimize distractions and help us mimicking view we naturally live when we are more clear and healed).
Devotional practices like song and chants, mantras, prayer, and some forms of meditation. (This includes all forms of mediation and other practices when done with devotion.)
Contemplation, inquiry and pointers.
Basic forms of mediation. For instance, notice and allow whatever is happening within content of experience. (And, with time, what it all happens within and as.)
Training a more stable attention, which helps us in spiritual practice and all areas of life.
Gratitude and forgiveness practices, and working with projections, like some forms of prayer (“thank you”), all-inclusive gratitude practice, Tonglen, and ho’oponopono.
Body-inclusive practices like dance, yoga, tai chi and chigong.
Subtle-energy practices through any form of inner yoga, and as found in traditional Indian yoga, tai chi, and chigong. (I would include Vortex Healing as an example.)
And (emotional) healing practices to remove blocks to noticing what we are and living from it.
Of course, I say these are more universal and timeless, but I am very aware that different traditions emphasize these differently, have different ways of doing each of them, and that this list reflects my own preferences, interests, and what I have found useful and helpful.