Formulas that remove a wall of helper columns, and when a helper column is still the right answer

A sheet with fifteen helper columns is usually three formulas that nobody knew existed. The ones that do the most work.

• A single formula that fills a whole column rather than one per row. Write it once at the top, let it expand down, and new rows are covered automatically. This alone removes most helper columns and every "I forgot to drag it down" bug.
• Query-style filtering and aggregation. One expression that selects columns, filters rows, groups and sorts, replacing a filtered copy of the data plus a summary block beside it.
• Lookups that return several columns at once, rather than one lookup per field.
• Conditions evaluated inline instead of a column of intermediate true and false values.
• Unique and sort as formulas, so a list of distinct values maintains itself rather than being a pasted snapshot that goes stale.

Where the wall usually comes from
Someone builds a column at a time while thinking, which is completely reasonable, and then never goes back. The sheet works. It is just fragile, because every one of those columns is a place a formula can be missing on row 4,000.

When a helper column is still correct

• When the single formula becomes unreadable. A clever nested expression nobody can modify in six months is worse than three obvious columns. Readability beats elegance in anything other people touch.
• When you need to see the intermediate value to check the logic, which is most of the time while building.
• When performance matters. Large arrays recalculating on every edit can be slower than a static column.

The practical rule: build with helper columns, then collapse the ones that are purely mechanical and keep the ones that explain something.