A tactical line is different from a concentrated battle fleet

Did navies abandon the line of battle when they adopted task forces?

No. Ships could form a tactical line within a task force even when the whole fleet was dispersed among separate operations.

Ships could still form a tactical line without a navy gathering its entire battle fleet for one decisive engagement. Cape Matapan provides an example of ships forming a line within a smaller operational force. Japanese interwar doctrine came closer to the older decisive-battle model, with submarines, destroyers, and cruisers expected to reduce an approaching American fleet before the main battle line engaged. Most other operations were better organized through task forces assembled for a particular mission.