I also use regularly miller/mlr with files having 1M+ lines and I never had problems with the hardcoded processing (i.e. "verbs") nor the DSL language which is know to be much less efficient compared to verbs.
Both visidata and miller are essential tools to process/view CSV/TSV files, way better than LibreOffice or Excel in terms of performance on large files.
Both visidata and miller are essential tools to process/view CSV/TSV files, way better than LibreOffice or Excel in terms of performance on large files.