I often use grids when flex would do just to take advantage of the grid gap features. Once the more general gap feature lands in most browsers I’ll probably start using flex more again.
Granted I'm mostly working on business apps, not a lot of complexity there layout wise, flexbox works great for that, and it's not a heavy lift for someone to learn it.
Grid is absurdly more powerful for full-page layout than flexbox (which is amazing for individual columns or rows). Especially once we start getting subgrid. The common comparison is 1 dimensional (flex) vs 2 dimensional (grid) layout.