One thing I learned was, that there is no compatibility. You can load some files from Excel, but to get something done, it's better to start a new file from scratch and import the data from csv. As soon something is more advanced (like configuring an axis of a diagram) it's all different.
Most important - CSV-Import in Calc is something that works just fine in LibreOffice, while the CSV-import in Excel has always been hardly bearable.
Of course, we cannot always help, sometimes the slowdown is due to increased feature or stability or conformance, but often we can improve things greatly.
As always, the behavior seen on some Linux distribution for some application may not match at all the experience on other distributions.
I always compile LibreOffice from sources (in Gentoo) and I have not noticed any performance problems, and most of my text documents or spreadsheets are quite large. It is true that currently I use it only on decent computers, but in the past I have used it even on several generations of Atom CPUs, from Pineview to Gemini Lake. Even on those there were no performance problems, at least not with Writer and Calc.