Distributism is, basically, the doctrine that "ownership of the means of production should be spread as widely as possible among the general populace, rather than being centralized under the control of the state (state socialism) or a few large businesses or wealthy private individuals (plutarchic capitalism)."
Note that Distributism is, fundamentally, a consequentialist doctrine - i.e., it seeks to maximize a certain ideal end-state-of-affairs viz., the widest possible distribution of ownership of the means of production - while leaving the means by which this is accomplished pretty much up for grabs.
And that, in the end, is what's wrong with distributism.
Given the vast disparities in productive potential found in nature between individuals, between ethnicities, between races, and so on and so forth, the only means of avoiding the concentration of ownership of the means of production in the hands of relatively few individuals, ethnicities, races, &c is to build a gigantically powerful centralized state which doesn't mind resorting to main force, whenever necessary, to bring about that goal.
Trouble is, once that gigantically powerful centralized state gets built - who do you think stands the best chance of taking charge of it?
Distributist philosophers? or, say, for example...Wall Street Banksters?
The question answers itself.