The reasons are, I think, more profound than Michael Gallagher suggests. He seems to think that the problem is one of individuals.
I have no experience with the ULA but considerable with two forerunners, the Socialist Labour Alliance (1970-1972) and the Socialist Labour Party (1977-1982). Each, like the ULA, had at least two Trotskyist groups and a number of members with no specific group affiliation. This might have worked if the unaffiliated members had been the overwhelming majority. But their numerical weakness meant that the groups dominated the life of the organisation.
In the original article Paddy Healy refers to Trotskyist groups’ struggle for dominance as an international phenomenon. Sociologically it may be a struggle for dominance. But it is fought as a struggle for the correct programme or policy, which acquires a totemistic value: the adoption of correct ideas becomes the key to acquiring mass support. In this they ignore Marx’s dictum “Every step of real movement is more important than a dozen programmes”.
But the question would remain as to the perspective in which real movement was envisaged. It would be encouraging if there was evidence that those debating questions like left unity were asking what the historic role of the left is to be. Personally I believe that the internationalisation, deconcentration, and deindustrialisation of modern capitalism in a world of shrinking resources make it no longer possible to posit either a workers’ revolution establishing a workers’ state or a parliamentary road to the traditional concept of socialism. But that is another whole argument.