If you look at this from an objective analytical analysis perspective:

Switch games released this year:

New Mario game + free port add-on content

A new installment in the acclaimed FF spin-off, Bravely Default 

Grabbed by the Goblins: Reserection 

A new installment in the acclaimed 3DS franchise, Monster Hunter Triple Cross Tekken 

And then you have Xbox:

The Medium (74 on oprahcritic)

Granted, it fairs a little better on Playstation:

Knack 2 remastered backwards compatibility update

And that's it. I think the games speak for themselves quite frankly. 

There are no PS5's or Series X to be bought and consumers don't seem to want the Series S since it's readily available everywhere. The whole industry is having issues right now, lots of converging factors have led to massive shortages and crazy price hiking on lots of products and components, such as GPUs, consoles, and even certain laptops. In addition, there are reports of slight RAM shortages and looming troubles for the manufacture and distribution of SSD drives and similar components.

TLDR; you can't sell what you don't have.

Because they are new.

Systems don’t just sell 400k+ right out of the gate, a sales curve goes up for a few years, peaks, and then goes back down.

Switch is on obsolete processor node (now 16nm without 3d AFAIK), whereas PS5 and the Serieses are at 5nm.
As it was when it when it was launched at 20nm without FinFet while PS4 Pro / One X were at 16nm with FinFET (3d) .
The newer nodes is normal companies want to be for performance/watt reasons, and so is most crunched while older is not.
Switch was already on strong trajectory so Nintendo likely already made strong orders so doesn't have supply problems.
Switch definitely isn't competing for the same factory production slots as PS5/XSn.

PS5 and Series X|S are selling about the same as PS4 and XB1 did when they were new systems. On top that, PS5 and X|S are still in what I like to call the "pointless sales period". All systems, including the Wii U, sell fairly well shortly after launch. PS5 and Series X|S don't even have any decent exclusives. Neither did the Wii U. It doesn't matter. There are some hardcore fans for all of these systems. They will buy a system for no other reason than they just are in love with the company. Personally, I am waiting until the end of 2021 to really start looking at the data seriously for these systems.

Switch, on the other hand, is something else entirely. It's on track to become the best selling system of all time.

1. Supply constraints for the PS5 and Xbox Series S/X
2. High demand in general for the Switch

Most likely it will.

I actually saw Xbox Series X out in the wild today, for the first time since launch.