In my last testing of powerpoint documents, I think FreeOffice/Softmaker Office got the closest on a consistent basis. But none of them were very good.
WPS Office would occasionally open one better than others but, on balance, compatibility was poor.
Most of the toolsets that are valuable to orgs (complex derivative formulae in Excel) arenāt available in the web versions. Itās good enough for doing a bit of home accounting or writing a letter, but not much else.