I think Flexbox is so much worse than CSS Grid. If Flexbox makes sense to you, it I don't think it should be that hard to learn CSS Grid, you'll already have many of the properties you need to understood learned. Grid just works properly in 2 whole dimensions where Flexbox sort of gives up after 1 and a half dimensions.

I know grid. It doesn’t do what I want, so I don’t generally use it.