I think GameCube looks better in retrospect, but living through it it had a trash release schedule compared to the other consoles, where it only got SOME of the big games, oftentimes they were nerfed in various ways (because the game either relied on having 4 triggers and/or clicky analog sticks or the game had a bunch of licensed video or sound that was removed, compressed to hell, or shortened.
Also, the Nintendo library was kind of hit or miss then. There were some highs like Metroid prime, but it had the worst 3d mario, and both the Zelda games were pretty mediocre. And rares output was bad and almost nonexistent.
It had some very very good games, but they weren’t coming out that frequently.
Also was missing GTA which was absolutely tremendously huge at the time.
Metroid Prime, F-Zero GX and Paper Mario 2 are some of the best Nintendo games ever made. Compare to nowadays, where they struggle to get a non-cartoony 3D project like Metroid Prime successfully developed.
Wind Waker and Sunshine were flawed, but at least they pushed for new tech and didn't rest on their laurels like New Mario Bros. 5 or whatever. Luigi's Mansion and Pikmin left room for improvement, but I'd be shocked if ARMS has the same staying power as these franchises.
GCN had everything that's still going on today, like Fire Emblem, Smash Bros., Mario Party, Animal Crossing, etc. Yet unlike later systems, GCN didn't stop there and still provided so many others things like everything I mentioned in the beginning, plus Wave Race, Jungle Beat, Eternal Darkness, Mario Strikers, Wario, 1080, Battalion Wars, etc. Not everything was an earth shattering hit, but at least they went beyond 2D platformers, party titles and animu. On top of that, they secured high-tier franchises like Star Wars and Resident Evil to further diversify the library. The closest they ever got to that again was Bayonetta, I guess. Yet GCN also had lower scope 3rd party exclusives like Tales of, Monkey Ball and so forth.
People hyped up the frequency of the first one or two years on Switch, yet the amount of critically acclaimed exclusives on GCN objectively was higher and had a bigger amount of genres. I don't know what your benchmark for Nintendo is, if GCN stands for bad frequency. Certainly can't be N64 or WiiU (LOL) either. Yes it missed out on many big games like GTA, but it had full- or timed 3rd party exclusives and several games were best on GCN. Lots of quality from Capcom, Sega, Namco... Many other ports clearly weren't superior - but that situation was still a hell of a lot better than to celebrate a platform becoming the dumping ground for fullpriced 5 to 20 year old games (of which some are still shit versions like Witcher).