Dropbox proactively communicated by email sent 26 January 2022 that it was aware of MacOS 12.3 compatibility for "online-only" files. Dropbox's email helpfully identified that "For this release, Dropbox doesn’t have full support for online-only files just yet. We’re actively working on full support, and the beta version will begin rolling out in March 2022."
Dropbox continues to make files on demand optional. OneDrive instead made files on demand compulsory, and did so without any notice.
OneDrive did not send any similar communication to Dropbox. Instead, it silently rolled out a release which became online-only, which was (and remains) buggy.
It appears quite clear that Dropbox has far superior communication with customers and doesn't pull the rug out from underneath them by removing critical features without notice.
If Apple deprecating kernel features is impacting OneDrive and Dropbox it is clear that Dropbox is able to handle the changes orders of magnitude better than what the OneDrive developers can.