Probably because of cartridge space.

Or the PS3. Really, people forget the strange design of the PS3.

But really all I read from your explanation is, that it isn't about architecture, it is about power. I agree in a way, since the Wii Nintendo decided to have lower specs than the competition. There is a reason the PS3 and the 360 were called HD-twins: power was similar enough to make porting games between easy enough (such low-effort ports usually left the PS3 at disadvantage, the strange architecture needed special consideration to fully utilize, so low-effort ports perfomed bad).

But generally people completely go bonkers on the name of the CPU. I'm a programmer, and I can say I couldn't care less. The compiler makes every CPU the same, except you need some special programming, as the SPEs of the Cell in the PS3 did (for which reason they were often ignored or underutilized). For gaming also graphic is more important, but this century the programmers less and less use the graphic card directly but instead using high level APIs. And as you said, Nintendo home consoles had pretty standard graphic chips.

So in conclusion: neither Wii, nor WiiU or Switch used an especially strange architecture that makes porting difficult. They all had less power than their competition, which indeed can make porting difficult. Also, Wii and WiiU had bad engine support (Switch has surprisingly good support in that department), which actually has WAY more impact than the CPU. Unreal Engine for instance supported Playstation since the 2, XBox since the 360, but no Nintendo console before the Switch.

I never understand why non-programmers get excited about the selection of the CPU-architecture, as every programmer don't care anymore as compilers support everything. The LLVM compiler targets X86, X86-64, PowerPC, PowerPC-64, ARM, Thumb, SPARC, Alpha, CellSPU, MIPS, MSP430, SystemZ, and XCore. The GCC targets even more, including some strange things. And there are many more C++-compilers out there (these are only very forthcoming with informations).

Same reason as before. The system is too weak for most of the AAA games.
Most devs don't want to tone down their games only to make it barely run on another system.

The Hardware is a issue again most likely.
Even if for Nintendo the "switch" is close to its competitors at around 1/5th or so the power of the others, its probably still a big hurdle to overcome.

"What else is it going to take to be listed with the other boys on every game announcement?"

a console thats like 80% atleast of the other two?
When PS5 comes out and is 10 Teraflops.... Nintendo cant come out with a Switch 2, thats less than 1/10th.

The problem is you cant make a handheld thats able to funktion in those power ranges.

Probably not.
Market is what? 3.3m Switch's and 6m PS4's in japan.
So Switch accounts for 1/3rd of the total home console market there.

And in another ~2 years, it ll probably be about equal to the PS4 in sales numbers (thus being ~1/2 of the market).

This.

Yep.

Too much work to downgrade, too big downgrades for developers feeling comfortable porting their games.
Its  gonna limit what "can" realistically be ported to the switch.

Its not because 3rd party hate nintendo, as some have written.
if its easy to port (hh+dock mode, make it harder) and can add extra sales, 3rd party will be there. If there not, its beacuse its not worth the effort to port it.

u got doom. And everything else is more like a interactive movie than a game.

I don't get that much exited about the name of the architecure. But at the time when Wii U release there were some not so bad low power x86 CPU at the market. And you still have to do different optimizations.

Making ports as easy as possible doesn't seem to be a bad idea.

The Switch architecure being a more or less stock Tegra also seems to have made engine porting faster, easier and cheaper than on Wii U.

These are 2 things involved here.
1)These are Holiday sales, so of course the system will sell.
2) This is relatively still considered a NEW CONSOLE LAUNCH.

Give it till lets say march when sales come back to normal, then lets see how the Switch does. Developers have been burnt by Nintendo consoles in the past you know.