Even with Hadoop, there's still algorithmic decisions that you have to make like whether to choose a stripes or pairs strategy when synchronization is needed[1], or choosing appropriate data structures for real time queries [2]. Sure something like Hive and Pig might work well enough for certain queries, but for some of the more complex queries where writing bare MapReduce or Spark is needed then these data structures and algorithms concerns pop up quite fast.

[1] https://lintool.github.io/bigdata-2018w/slides/didp-part02b....

[2] https://lintool.github.io/bigdata-2018w/slides/didp-part09b....