Yes. Nintendo's output so far on switch in 2018 is a testament to why they need a budget handheld device. Their game releases has been laughable in 2018. I am a huge Nintendo fan and I purchased 1 first party switch game in 2018 (LOL, I don't even think that ever happened even for wiiU) and it's Mario tennis which is a third tier franchise (LOL again). They're trying to camouflage their poor output of games with a bunch of full-priced ports which is inexcusable and are essentially punishing people who supported them through and through in the wiiU days.
So why does all of this matters? Because a budget handheld would allow them to release games on a more frequent basis due to the need for smaller teams and cheaper budgets. This would allow Nintendo fans like myself to not have to wait 4-6months (or more, we haven't had a AAA Nintendo release since October 2017 which is ridiculous) between each major Nintendo first party releases. In the wiiU and 3ds days, it was almost always the case of when there was nothing to play on wiiU, something would release on 3DS and vice-versa which in the end means more money for Nintendo. Not to mention, a budget handheld device would almost certainly sell very well for them.
/end of rant
You know, I think the idea that Switch has a disappointing library is a lot more respectable than most on this forum. It's pretty sad that this kind of reception to the Switch is practically outlawed or laughed at immediately. However, a lot of your comment is pretty unreasonable.
You're absolutely right that the "unified library" is taking a lot longer to really show it's claws, but making a separate platform is not the answer. Firstly, because the generational leap between the 3DS and the Switch would be such an awkward middle phase. It would be like the Vita, with very few of the benefits of a dedicated Nintendo handheld (low cost for games and thus faster development times), and bad quality "console-like" experiences. Having something between a 3DS and Switch that would stand out when the Switch is already released would be hard, because it wouldn't have any of the real advantages of low cost handhelds or high cost hybrids (which already aren't really "high cost" as it is). We already see that Switch games can run on 3DS when they are dumbed down far enough (Fire Emblem Warriors), and we've already seen that phone-quality assets that are cheap to produce can look fairly pleasing to the eyes on a console (Pokemon Let's Go). What would a compromise between a 3DS and a Switch offer? With all due respect to their developer prowess, Nintendo titles are already incredibly cheap in comparison to most other AAA devs.
Secondly, ports on Nintendo handhelds have a long history. Look at the Gameboy Advance: It's considered by many to be one of the best consoles ever made, yet it's best selling titles consist of the likes of Mario ports, a Mario Kart game that is practically a port (from what I know, could be wrong), Zelda ports, and third party collections. And is it a coincidence that during the Gameboy Advance era we saw the first Pokemon remake instead of a second new mainline title? Or how about 3DS? With it's ports, remasters, half-sequels, etc. Donkey Kong Country Returns 3D, Star Fox 3D, The Legend of Zelda: Ocarina of Time 3D, The Legend of Zelda: Majora's Mask 3D, The Legend of Zelda: A Link Between Worlds, Yoshi's Wooly World, Hyrule Warriors, Fire Emblem Warriors, Mario Party Top 100, Metroid: Samus Returns, Yoshi's New Island, Smash Brothers for 3DS .... when you cut all that out, yeah, you could make the exact same point for GBA and 3DS. Is it really fair to say that Nintendo didn't have problems supporting consoles and handhelds in the past before the Wii U and 3DS era? Because really, I don't see it. The Game Boy lasted 12 years and didn't hit the peak of it's stride till well after release. I imagine there were times where people had little to play in the span of 12 years. The DS had the most bountiful library of any Nintendo handheld, but at the cost of the GBA's lifespan. It had great 3rd party support because it was an innovative device ... but it's hard to say if we'd ever get something like that again.
You're right that you'd probably get more out of two Nintendo consoles in one year exclusive-wise than what you'd get from Nintendo with the Switch. However, that has more to do with release schedules than content. When Nintendo has to support two systems, they rush out projects sooner. That's why 3DS has so much unoriginal content or re-used concepts. Switch ports are just more upfront and apparent. But you still had large spans of time where nothing came out in the past. With the release schedule right now, we can assume that while there are going to be some dry months as far as exclusives go, we won't have near entire years like we with the Wii U and even the Wii (or the 3DS, which got to the point where there would only be one big original game from Nintendo near the end of it's life). The Switch is supposed to have a consistent release schedule that results in a longer life span, and unfortunately that might mean some titles get pushed back.
To summarize once and for all, if your criteria is how much you have to play, then I have to call into question why you think past console cycles were that much better. There were more games ... but for consoles like GBA and 3DS, that metric relies heavily on the same kind of titles you complained about (ports, half-sequels, etc). Not only that, but those systems were at their peak when they were put next to the Gamecube and Wii U, which are infamous for being at times barren. The Gameboy was next to both the NES, SNES, and N64 .. but it hit it's most popular point when the N64 was out, a system which also had a very barren release schedule. The first few years of the DS and the Wii was a near perfect combo, but look at how poorly Nintendo supported the Wii in the last 2 years (you could argue even 3). If you brought up major third party releases maybe you could make a point, but you didn't. This has always been a problem for Nintendo, it's just now the solution isn't to pay for two consoles.