It's not even really particularly true, at least the implied criticism. My work uses M365 and Microsoft Office worked fine, both online and offline versions. Email stopped working, but AFAIK Open Office doesn't make an open source email server.
> AFAIK Open Office doesn't make an open source email server.
How do you draw the line? There is at least one LibreOffice developer who also contributed to Dovecot.
Yes, I made an assumption, arguably unfounded, that MS365 had been affected by the recent issues.