The phrase "a true substitute" is correct and usable in written English.
It can be used when discussing an alternative that genuinely fulfills the role or function of something else.
Example: "In this recipe, almond milk is a true substitute for cow's milk, providing a similar texture and flavor."
Alternatives: "a genuine replacement" or "an authentic alternative".
This is why a 401(k) is not a true substitute.
But analysts say such sales are still too small to measure and cannot yet be viewed as a true substitute for purchasing music on CD's, tapes or records.
And the Xbox won't be a true substitute for everything viewers can get through their cable boxes because content rights will have to be negotiated for some shows before they can be watched through the console.
Pfizer says the strips are not a true substitute for rinsing with Listerine, because the liquid version tends to be more thorough as a germ killer than the strip.
But Dr Richard Vautrey of the British Medical Association warned: "There is a danger of looking at one element of body fats in isolation and reaching conclusions that challenge the assumption that there is any true substitute to a healthy diet and lifestyle".
Later on, Uber launched Uber X, a lower-cost alternative that made it a true taxi substitute and made its global ambitions more apparent.
But despite its mainstream success, questions have always lingered about whether the popular tablet is a true laptop substitute -- especially for the business set.
Similarly, they're now flogging "mushroom mince" made from those same ugly mushrooms, which is vegan, but also it's £1.50 for straight-up chopped mushrooms in plastic packaging – not a true mince substitute by any stretch of the imagination.
There is no true substitute for butter, which is traditionally brushed on each layer of dough to impart richness, flavor and a delicate crispness.
Messi, Suarez and Neymar scored a scarcely believable combined total of 122 goals last season, and their consistent brilliance has left Pedro lagging well down the pecking order, relegating him to true substitute status for the first time.
It is a challenge to design large-scale human nutrigenetic experiments and an even more daunting task to get them adequately funded in the current environment, but unfortunately there is no true substitute.
