It depends on your needs.
With my emphysema, I like a lot of closely spaced gears so I can keep my cadence in a very narrow range, even though I don't have hills where I live.
My 2 bikes are 3x9, using 22-32-36/38 cranks & 12/13-23 cassettes.
I typically just use the middle ring, but at times have had to drop to the granny ring in severe head winds. Still glad to have close spaced gears there too.
Large ring only gives me about 1.5 gears higher, but is useful at times when I'm out of city traffic and have the rare tail wind. I simply can't spin higher gears without "gassing out".
Others are happy with ONE gear.

There is no "correct" answer!