I agree. It's fairly common for experienced front end devs who have been bitten by browser incompatibilities in the past to wait several years to adopt the latest CSS techniques. The "old techniques" often work very well.

Most likely if you had asked me "why flexbox and not CSS grid" I would have said "because flexbox is able to perfectly well support this use case, and I'd rather not introduce a dependency on a less well supported CSS feature unless I need to".

I personally tend to prefer using the oldest (within reason) CSS feature that lets me accomplish a task. Or I'll pick the one that best conceptually maps to the task I'm trying to accomplish, if there's a significant difference.