I like narrow commanders because it forces you to use different cards than what you would in a generic deck and makes you think about what off-meta cards might shine. Pick a tribe/mechanic/strategy and tailor the deck to that specifically. If it's too narrow, you can add a sub-srategy to still creatively constrain the deck without opening the floodgates of genericism.

When you leave the deck open-ended mechanically, it becomes a good-stuff pile, as others have mentioned. This get boring and same-y. The other aspect is that generic decks often are harder to trim down in card choices as opposed to narrow builds where it's more obvious which cards will put in more work.

Personally, I have Skullbriar 1/ 1 counters, Hapatra -1/-1, Zur Astral Slide, Will/Rowan spell copy, Yidris tempo-cascade, and high-power Locust God combo, and Brudiclad tokens as my more narrow decks and they're a ton of fun to play.

I also have Muldrotha good stuff which I'm liking less and less because it doesn't feel like it does anything interesting compared to the other decks.

I like narrow commanders because it forces you to use different cards than what you would in a generic deck and makes you think about what off-meta cards might shine. Pick a tribe/mechanic/strategy and tailor the deck to that specifically. If it's too narrow, you can add a sub-srategy to still creatively constrain the deck without opening the floodgates of genericism.

When you leave the deck open-ended mechanically, it becomes a good-stuff pile, as others have mentioned. This get boring and same-y. The other aspect is that generic decks often are harder to trim down in card choices as opposed to narrow builds where it's more obvious which cards will put in more work.