1. It looked like a child's lunchbox, so it had the reputation as being a kiddy system.
2. The controller was ridiculous: unusable d-pad and z-trigger, really weird L&R shoulder buttons that made a lot of noise, the weird face buttons which prevented a lot of button combos available on the N64 and SNES, and the poor quality analog sticks, especially the right analog.
3. Lacking features, including the DVD player that was heavily in demand, online functionality.
4. Most importantly, it had no killer apps like Ocarina of Time, Mario 64, Mario Galaxy, or even a Wii Sports.

It was just plainly not a very good system. People today often forget how bad the GameCube era actually was, I would say worse than Wii U.

Absolutely correct. There were many ways to keep Playstation from ever happening and only one way Playstation was going to happen. Nintendo picked the one option that allowed Playstation to happen and it has been twenty-one years their bane.

Delaytendo always keeps coming back.

MS wouldn't have given up on the Xbox brand if the Xbox had only sold 10-15 million units and if Cube had been more successful: they lost a lot of money with the original Xbox, yet they still made the 360. If anything, a more powerful HD nintendo console would have been destroyed by the ps3/360 because it would have lost third party support for the same reasons the Gamecube lost third party support: because western publishers don't think that their games can sell on intendo consoles. Honestly, without the Wii/DS, who knows where Nintendo would be right now financially speaking.

PlayStation had Metal Gear Solid, Crash Bandicoot and Gran Turismo so it would have still sold a lot more than N64 even without FF 7.

If I remember well it has two purposes: 1 - to make it easier to carry and 2 - to give the owner the impression of a friendly/acessible product. I was designed more like a "marketing message" than a "useful feature".

Of course, people would eventually find different uses for it, like using as a kettlebell for exercises,  making contests of Olympic Gamecube Throw and Gamecube Curling or using it as a fashion acessory:

And by the way... the WiiU actually sold better than the Dreamcast by now, in both hardware and software. Still a looong shot to be considered even a moderate success, though...

Really, everyone knows about the N64 and its decision to stick with carts, but one seriously underrated factor was the delays that pushed it back well behind the releases of its competitors.

While people were anxious for an optical media console given what it promised, Nintendo would have done faaaar better that gen if they'd simply released their console on time.

The Gamecube was a huge blunder as well, mostly as they didn't want to rely on someone else's proprietary format and went with the small disks. It's often forgotten today, but the reason the PS2 set the all-time record for console sales was not due to gaming, but because everyone and their mother was buying them as the best option for a DVD player. Sure, they would have sold very well either way, but that pushed them through the stratosphere, as they were often the best deal available for playing DVDs.

Otherwise, the Gamecube actually maintained rather strong 3rd party support, had superior hardware to the PS2, and looked gorgeous (I was just watching someone playing Pikmin 1 last night and was amazed by how great it still looks). If they hadn't lost so many players the previous generation and actually provided a DVD player with the Gamecube they could have done much better than they did.

Still, the one thing that secured a place for Sony (many were skeptical when it was first announced) and won people over in droves to the Playstation was, to put it quite simply, Final Fantasy VII and the FF franchise overall. This defection (they'd only been on Nintendo consoles to that point) was due to Nintendo's decision to stick with carts, and people just had to have a Playstation when they saw those games (I personally made the jump for FF Tactics and played VII/VIII/and IX to death).

Overall, then, it's impossible to overlook the delayed release of the N64, and Nintendo's unwillingness to use someone else's proprietary format with the N64 and Gamecube really screwed them. If, for instance, the N64 had simply released on time and later the Gamecube also released on time with a DVD player, they'd have been in far, far better shape than how it turned out even without Final Fantasy.

On the bright side, we got two of the best multiplayer consoles of all time, and anyone who was around them has fond memories of them. :)

For the record, btw: Sony and Microsoft weren't going anywhere. This was the first time companies with almost unlimited piggy banks joined the fray, and they weren't afraid to absorb any necessary losses to the same extent that Nintendo was. Sega tried their approach and it sunk them. To this day, the Xbox brand hasn't turned a profit for Microsoft, but they clearly just like having a brand for a company that is otherwise mostly known for Operating Systems.

Sony's piggy banks dwarfed Nintendo at that point, despite Nintendo's success. Sony was on top of the world in multiple markets in the 90's.

Basically, Nintendo didn't read the fine print that Sony slipped in (this whole episode reads as one experienced company taking advantage of an amateur) and likely couldn't have had much success in court given the language of the agreement clearly favored Sony. Nintendo had little choice but to back out at that point, and Sony had learned all they needed to about making a video game console from the experience.

Platinum should have been the gamecubes primary color, a nice evolution from Nintendo's typical gray and just a more premium look in general.  Also would have set  itself apart from the other mainly black systems.

ranking color from best to worst (subjective obviously)

Platinum

 Black

Orange spice (loud, but acceptable)

Purple (kiddie AND feminine)

Really a horrible decision... when the buttons are also colored,  there needs to be a more neutral main/background color, so purple gave it the fisher price look.  Worked for GBA because all the buttons were a neutral gray, but the gc console looked like a mess.

While there used to be trash talk, and typical console-war jabs  from fans about Nintendo being "kiddie", the Barneycube  really gave confirmation to that stigma, and made it easy for the encroaching Microsoft.

Nah, I believe it all went wrong with the SNES. Simply because Nintendo enforced such one-sided policies on third parties. After that, third party developers were all too happy to jump onto the playstation and forever forget the Nintendo. I think that to this day, third parties continue holding a grudge against Nintendo. Even if Nintendo did make a platform designed for multiplatforming the other systems, they still wouldn't get those games.

Nintendo's only chance at a revival is the way they've been going. It's either Blue Ocean or third party.