I am sure that it is counter-productive when Christians give prominence to the Holy Trinity in describing the nature of their faith - to the point that it seems quite common for a statement of Trinitarianism to be the very first thing on the list when some Christian churches make a statement of 'what we believe'.
This is a mistake in so many ways. Fundamentally it is a mistake because these Trinitarian statements are (almost always) formally and literally meaningless - and can (presumably) only be made-sense-of at such a high level of abstraction or spiritual development as to be irrelevant to public statements of faith.
At the level of public discourse, especially of secular discourse, standard Trinitarian formulations sound either confused or insane - which is not a useful impression to create.
Furthermore, these Trinitarian formulations are all-but-irrelevant to the Christian devotional life - and indeed have been a terribly destructive force in the history of Christianity - provoking some of the saddest and most futile yet lasting schisms - such as the 'monophysite' controversy which was a quibble over words that led to horrible persecutions and the first major and still effectual split in The Church.
Against such an horrific backdrop, the Trinitarian formulations such as the Athanasian Creed achieved church unity at the cost of what could charitably be called incomprehensibility, or uncharitably be called obfuscation.
But all this should have nothing to do with a modern secular materialist who is making some tentative moves towards Christianity, and browsing the internet or picking up a leaflet, comes across a church that seems to be (and indeed is) genuinely Christian - and then gets immediately confronted by some Trinitarian formulation as if this was the core and focus of the Christian life...
This is an unforced error by the real Christian churches, a self-inflicted wound; or what people nowadays miscall 'shooting yourself in the foot'.
I cannot imagine anything more off-putting to an incipient Christian than to run-up-against something about the Holy Trinity - like a high jump or a stumbling block or a tangle of thorns which must somehow be got past to become a Christian.
I only got past it by accepting that it was all 'a mystery' - if Aquinas didn't understand it, then how could I? - but the problem was artificially created in the first place.
The Holy Trinity is a matter about which evangelists should answer questions honestly and as best they can - but at the level of answering questions.
To raise the subject of the Holy Trinity, upfront, without provocation - deliberately to highlight the problem, and then utterly fail to answer it acceptably is the worst of possible worlds!