It is true that Talmud study is not the most practical way to reach halakhic conclusions (cf. here). It is also true that many authorities held that rather than study Talmud, the most important thing to prioritize in study is applicable halakha.
Nevertheless, Ashkenazi yeshivot historically focused nearly exclusively on talmud, because they were designed to promote the small percentage who would need that knowledge in order to be rabbis and poskim. The educational system was not designed primarily to accommodate the other 99%.
In the words of R. Dr. David Katz:
Obviously, not every student was capable of mastering such material. Whatever the ideological reasons, there can be no doubt that society felt comfortable with a highly elitist educational philosophy with an almost conscious, exclusive, focus on the production of a few gifted students at the expense of the great majority. 
Similarly, Dr. Ephraim Karnfogel writes:
The basic educational curriculum in Ashkenaz was structured with the hope that it might produce a young Rabbnu Tam. It was, above all, Talmudocentric...The communities felt no acute need for an educational system...that would address the needs of ordinary men .
And similarly Dr. Jacob Katz writes:
[Altohugh] only a small minority of students could hope to attain this ideal...the heder...was made subservient to the needs of the minority...Even if only a minority could actually engage in it, study of the Talmud was a primary value...The educational goals for the people as a whole, knowing the fundamentals of Judaism and the fulfilment of its precepts, were considered as no more than byproducts of an educational system directed to developing Talmudic scholars. 
 A Case Study In The Formation of a Super-Rabbi: The Early Years of Rabbi Ezekiel Landau, p. 104.
 Jewish Education and Society in the High Middle Ages p. 180, cited ibid.
 Tradition and Crisis p. 163, cited by Katz ibid.