Many of the files are XLSB, which is like XLSX except it stores sheets in a binary format. For reasonably large files, opening XLSB is much faster than XLSX.
Google Sheets straight up fails if you try to upload files in that format. No preview available and no option to work around. So I would have to open the file in Excel anyway.
Relatively new versions of LibreOffice are capable of opening simple files, but once you get into features like named ranges LO fails.
So even if the UI is acceptable, failures on data import force me to keep a copy of Excel around. Keep a VM with Excel for Windows around just in case files don't work in Excel for Mac, but I've used it maybe once in the last 6 months.
Google Sheets straight up fails if you try to upload files in that format. No preview available and no option to work around. So I would have to open the file in Excel anyway.
Relatively new versions of LibreOffice are capable of opening simple files, but once you get into features like named ranges LO fails.
So even if the UI is acceptable, failures on data import force me to keep a copy of Excel around. Keep a VM with Excel for Windows around just in case files don't work in Excel for Mac, but I've used it maybe once in the last 6 months.