"Is numbers just a "pseudoexcel" copy for very small jobs? I have never experienced this problem with excel."
"… might switch to windows and leave apple altogether if this isn't fixed."
Numbers is not, and has never pretended to be a copy of MS Excel, 'pseudo' or otherwise. It is a spreadsheet application, and as you've observed, is better for handling small data sets than it is for large ones. That's been true since version 1 (Numbers '08).
As SG has mentioned, Excel for Mac is available as part of MS Office Mac, and the current version of Excel works well in the current version of macOS. If you are exchanging documents with Excel users, or if you are working with large datasets, then it makes sense to use Excel, if only to avoid the translation of documents from .xlsx to .numbers (with a loss of or change to any Excel functions/features not supported by Numbers) to work on the document, then a second translation from .numbers format to .xlsx (with a loss of or change to any Numbers functions/features not supported in Excel).
"…if this isn't fixed."
Wrong audience for that request. This is a user-to-user support community. Apple supplies the space, but nether Apple nor its employees/representatives regularly read or participate in these communities. Fellow users can help with using the software as it currently exists, but they can't change software. Requests for a change in the software, whether to enhance features or to fix the bugs, need to be directed directly to Apple via the Feedback channel. In most current Apple Applications (including Numbers), you'll find a "Provide xxx Feedback" item in the Application menu (the one immediately to the right of the Apple menu, identified with the name of the active application).
Click that item, then make your request.
Brian wrote:
"…Must be fixed."
"…The app has an issue"
Hi Brian,
See the last two paragraphs above.
Regards,
Barry