The phrase "a lack of solidity" is correct and usable in written English.
It can be used to describe something that is not firm, stable, or reliable, often in a metaphorical sense.
Example: "The argument presented in the paper suffers from a lack of solidity, making it difficult to accept the conclusions drawn by the author."
Alternatives: "a deficiency in stability" or "an absence of firmness."
And there was a lack of solidity and an absence of guile which was truly worrying.
One study showed that in a group reading the same book, e-readers had a lower plot recall, which was credited to a lack of "solidity".
Despite his powerful mimetic skills, he has a lack of solidity, a preternatural detachment, that make him an implausibly engaged protagonist, particularly in dramas set in earlier, more granitic times.
On his return, however, a certain waywardness, lack of solidity and conviction and rhythmic vagaries were detected.
Pakistan's ambivalence toward the Afghan Taliban has also stemmed from a lack of belief in the solidity of the Afghan state.
While this not knowing can generate fear, my experience is that the lack of solidity in the Void is paradoxically the foundation on which I stand in the world.
There were glimpses of potential in Fraser Aird, moments of rashness and haplessness from Bilel Mohsni, an industrious if limited display from Ian Black, solidity from Jon Daly, a lack of substance to Arnold Peralta and the nagging sense that Nicky Law has misplaced so many of his certainties that he is cautiously plodding through games.
A few family physicians expressed a lack of trust in guidelines either because they questioned the "solidity of recommendations" or because they were industry sponsored.
Trapattoni's major team selection decision has seen him opt for the solidity of Leeds midfielder Paul Green - despite a lack of popularity with fans and pundits - in the centre alongside Glenn Whelan.
A lack of entrepreneurship.
A Lack of Professionalism.
