>Migrating contacts and calendars is easy, thanks to open standards (unless you're migrating in bulk)
Ehhhhh, Workspace has a half-assed EAS implementation that works until it doesn't (just had a client where it stopped exporting all his phone numbers, the data was still in Google but their EAS just wasn't outputting it). It's hardly an open standard but theoretically works for Outlook users migrating to Exchange.
Going anywhere else with an Outlook desktop user that actually follows the open standards (CardDav/CalDav) is extreme pain because Outlook lacks native support, so you need to use a plugin that will pull the data but not present it in the same way. The earlier mentioned client I moved to Fastmail and I still haven't figured out how to get his 'contact folders' to show and sync in Outlook without heavily customizing the views. Otherwise works in Android with DavX and iOS natively.
If it works. I tried to use Takeout to split an 18GB archive into chunks last month. After waiting all night for Takeout to prepare the download for me... it gave me a single 18GB archive to download.
I've seen more movement in the opposite direction, from M365 to Google.
Mostly from companies who chose Microsoft before G Suite became popular for business.
But maybe it's industry-dependent?
In any case, you definitely need consultants because it's a pain no matter which direction you're going. Not a decision to take lightly, and you're not going to switch again for another 15 years.
I generally see Google -> M365 given the severe poor suitability of Google Workspace for enterprise businesses. And given those businesses often need to run Windows & Office regardless, sticking to Google makes even less sense.
Migrating contacts and calendars is easy, thanks to open standards (unless you're migrating in bulk)
Migrating email and validating the migration is a HUGE pain and takes forever.
Data from any other Google service is basically unusable anywhere else. Yes, you can export it via Google Takeout, but they are all but proprietary.