[Macha]

I guess it depends on your past experience, but for most of the teams I've been involved in, it was basically a leap from floats to grids for page layout, with flexbox being a small scale option before and after.

[nightski]

Anyone that had to support IE11 probably avoided grid for a long time but could still use flex.

[meerita]

Yes. The more older the project is usually goes with the avoidance of CSS-grid and other features.