I deal with hundreds of API integrations involving various JSON, CSV, TSV, and XML files with mixed validity. My workflow: Notepad++ for a visual check -> Prototype everything in Excel. I give users a "visual", connect it to real data, and only then migrate the final logic to BI dashboards or databases.
Nothing else delivers results this fast. SQL, BI tools, and Python are too slow because they generally need "clean" data. Cleaning and validation take too much time there. In Excel, it's mostly just a few clicks.
PS: I spent 2 years (2022-2023) using LibreOffice Calc. I didn't touch Excel once, thinking I needed to break the habit. In the end, I did break the habit, but it was replaced by a pile of scripts and utilities because Calc couldn't do what I needed (or do it fast enough). The experience reminds me of testing Krita for 2 years (2018-2020) — I eventually returned to Adobe Photoshop (but that's another story).
PS2: About (Query + Pivot + BI). This allows you to process millions of rows (bypassing grid limitations). It also allows you to compress everything into an OLAP cube, taking up little space and working quickly with data.