So basically you want Nintendo to ignore expert players when they already have other 15 platform franchises for everyone, and just to push a few more units.

When you see Nintendo not releasing a new Metroid blame yourself :P

I think the difficult was expertly balanced in Tropical Freeze. What's wrong with a game being hard btw? It's far more rewarding to succeed after many tries.

I dont consider TF a hard game. As a whole, I dont consider DKC a hard franchise, so I cant quite agree with you there. If anything, platformers have a tendendency to be easy and that's not always a good thing.

I have no issue with difficulty levels in games, easy, normal, and hard modes shouldn't detract from anyone's experience.

I can guarantee you that isn't the case. The original DKC games were all much, much harder than either Returns or Tropical Freeze and all sold well. TF didn't sell quite as well because it wasn't the return of a beloved franchise and it's on the Wii U.

I wouldn't be opposed to the addition of an optional easy mode, but there is quite a lot in TF that already makes things easier. If you're having trouble, Dixie's team up ability turns enemies/objects into extra hearts that can stack on top of the full four, allowing more survivability, as well as items you can buy making you invincible for a limited window of time. With that said, DKC has made its name on being a hard platformer. Nintendo already has an easy platformer; Mario. Including an easy mode isn't likely to win many people over to DKC, because people who want an easy platformer are already playing Mario.

What's the wrong with dying over and over again? I beat Bucky O'hare on NES just before christmas (first time in more than two decades), it took me 1,5 to 2 hours just to beat the final boss - I just kept dying, and had fun.

The problem with games today is, that you don't die that easy (aside from some cheap deaths). What you describe isn't the game being hard, but the opposite. The game flows easilly, and when there's challenge, the jump feels too big and you die. You don't want to start again because sitting trough and maybe dying again isn't worth it.

I think Metroid Other M, for example, took 45 minutes before encountering  the first challenge in the game.

Yeah. Imagine how much more successful Dark Souls would be if it had FFXV babysitting difficulty level.

^

Let's give an invincibility mode on Dark souls while we're at it

The dkc franchise was never an easy walk. It was always pretty challenging, but it was never unfair.
Even the secret temple levels which are a pain in the ass are still manage able.

Don't dumb it down.

DKC's difficulty is perfectly fine. There is absolutely nothing wrong with it.