It's a video game, not homework. It doesn't need to "teach" anything.

Opinions are opinions.

Mine is that a good game teaches you how to play it. That's also a fundamental of good game design. Every time I go through a tutorial I cringe b/c its just evident of a lack of the prior to an extent. 

An invincible mode and a tougher mode only add to the game. If you don't want to play them, then don't. So stoked for this game.

I look a Epic Yarn and Wooly World (which I assume has the same immortality principle behind it).

I'm like 

I don't have a problem with that because the game is designed around it. 

But here its like, if you wanted to make the game approachable, design it, don't just flip a switch no effort on the devs part, whats the difference from watching it on a lets play for the gamers, nobody the player doesn't really benefit from it.

In Star Fox, its especially egregious b/c of the game's own design.

Addendum: Responding to it on a matter of preference is pointless and boring, because the options don't detract from the game, option argument is always the answer. Repeating it ad infinitum doesn't go anywhere. What I think is more valuable and interesting is debating it on the matter of principle.

If you must see it as a learning process, then this is still learning. You learn what lies ahead so you can then use that knowledge to inform a later playthrough without invincibility. Observing and adapting, that's learning. It can also help you learn the controls while you're observing. Punishment isn't an essential component of the learning process.

Why would you need this? What's the purpose of buying a game if it doesn't present some sort of challenge?

The internet, nuff said

Shoot'em ups regularly offer such a mode (granted: no high scores will be saved or they are on a separate list, nothing's unlocked, etc. and I don't know if Nintendo is doing the same thing) and just because this is Nintendo and a bit popular, all the "hardcore gamers" are going crazy about it while they never care about unpopular games and therefore don't know stuff about games.
If you don't understand the purpose of such a mode, no need to play it or even judge it (although it might make less sense in a game like Starfox that is a very easy type of shoot'em up). It's not like the devs spent weeks on this, it's done within minutes.
I love hardcore gamers and gamers who act like they know what they are talking about.

Hmmm interesting.... There was a thread on here asking if "Gamers this generation are spoiled by low difficulty levels" and 70%+ agreed with that statement in the poll, yet the majority here are saying no.

Anyway options are always good, there's no problem with this at all.

This is just stupid, this is basically easy mode and we also know game will have some sort of hard mode, almost every game have difficulties you can choose, so why would someone have anything against this game having easy mode?!

Stupid reactions doesn't deserves own thread.

While that maybe true, the onus is on the developer/designer to make an option like that unnecessary, or at the very least design the game or option around it.

I'm reminded by practice mode in DDR which is nearly the same thing, which I used extensively while playing it.

The subtle difference is that there isn't a reward for completing a song in practice mode, its sole purpose is teaching because the reward is some parts actually beating the song itself, points, and other unlocakables. Here its justified.

Granted the details aren't clear on whether or not the game can be "cleared" in invicible mode, but if that is the case you are rewarded for just effectively nothing and a lot of the incentive to even play the game in a non invicible mode is lost. That is an option, do I agree with it? No. That's simply my stance on the matter.

And Punishment might not be essential to learning process, Reward might not be either, but it certainly makes things more engaging and interesting, which are certainly prime aspects of Fun.