There are many features of Excel that LibreOffice Calc doesn't support. Most importantly: structured references, VBA, PowerQuery. Not to mention its UI is very laggy even on powerful machines.
For real financial/business work, Calc is just not a serious player.
I have a spreadsheet I've been using since 2017 to track all my spending and savings accounts on a weekly basis, plus some trend analytics, plus some simple graphs on multiple sheets. A few hundred rows and columns, both entered and calculated values (simple formulas, nothing fancy). Haven't noticed any slowness. When I have some data to look at (like .csv or even .xlsx), I always use Calc. I work with Excel at work all the time, it might be faster on larger data sets, but Libre's Calc is more than enough for many use cases.
I think there is a recent performance regression but hopefully will be fixed soon. Hasn't affected me. Learn Python, much better than VB.
I even had to switch my reading list spreadsheet over from LibreOffice to Excel when the former started seriously lagging with about 250 rows total