Has Merge Join's Time Gone?

I have long thought of the hash join/merge join duopoly as reflective of the fundamental truth that basically all data-processing related algorithms are based on either hashing or sorting. Yes, we also have nested loop join, but that's sort of just hash join in disguise. Aggregation? Your options are sorting and grouping, or hash bucketing. Deduplication? Same deal. Union? Intersection?…