People always say this but the 90% doesn’t count. The 90% is easy. It’s the other bit that people hit and compatibility issues mean any non standard approach whether it’s fair or not will always, always get the blame.
Plus I dispute that libreoffice has even close to 90% of what excel can do.
Let's not compare the advanced options of Excel or how Excel bugs annoy me. There are loads of them.
Let's just compare what people do when they need a tool like Excel. That's when the 90 or maybe more % of people will do. That is what I do. Everything I do in Excel can be done on LibreCalc.
So it is true that LibreCalc can replace 90% or more, because not everybody needs those advanced topics.
Same for the other LibreOffice apps, Writer is good for almost everybody. As LibreDraw and others.