The phrase "are truly capable of" is correct and usable in written English.
It can be used to express someone's or something's genuine ability to perform a task or achieve a goal.
Example: "With the right training and resources, individuals are truly capable of reaching their full potential."
Alternatives: "are genuinely able to" or "have the true ability to".
From privacy and surveillance to our collective cultural record, where is the internet we are truly capable of?
As a result we lose touch with who we really are, what we are truly capable of and what matters most in life.
But if we are to learn the lessons of the Wilson plot, to realise what Britain's hidden powers are truly capable of, then these events deserve a proper reckoning.
The men in whom alcohol seems to increase efficiency... have little confidence in themselves, are so shy, so greatly subject to anxieties, that they are hindered in doing what they are truly capable of doing.
According to Steve Harper, the reserve goalkeeper, Pardew "read the riot act" to his team following last Saturday's fortunate draw at Reading and has challenged Newcastle's players to remind him what they are truly capable of.
It's possible to put the question of religious belief aside in "High" and have it ask only whether human beings are truly capable of change and, if so, what that requires.
Arlo makes an unlikely friend in his toddler pal, and "learns the power of confronting his fears and discover what he is truly capable of", according to the official plot synopsis.
A review for the BBC wrote that Hoffman had finally been given a part that showed "what he's truly capable of", but few witnessed this as the film had a limited release and earned only $210,000.
The new fixture, which maintains all the capabilities of its standard counterpart, is truly capable of sustaining loading in tension as well as in compression so that specimens can be tested for loading and reversed loading.
As a result, they settled for a mediocre existence and never became who they were truly capable of becoming.
"But the key will be constructing an Afghan force that is truly capable of taking the lead".
