I don't know if it's a generational thing, but we've had quite a few younger colleagues - early 20ish - join our company recently and quite a few (not all!) of them are remarkedly casual in their communication style.
Signing off emails with "thx" or using "yh" for yes. Very short one line responses with no To or sign off at all. And loooong response times unless you chase them via Teams. We're mostly hybrid / remote.
Is this a new communication style thing, or just our particular batch of new employees?