If total SW of PS5 is lower than PS4 yes I would consider it bad since WW it seems to be slightly better (independent of digital attach ratio), the problem is we don't have the data to claim it.

You think looking at the ranking is enough and I told you that if you looked at the Switch rank of million sellers you would have only 7 3rd parties, that would say that 3rd party sales is basically non-existent, would you agree with that? If not, why do you think looking at the 30 rank will tell the full story and show close to full sales of PS5 SW sales? In Europe a lot of big IPs were quite low on the annual rank. FF16 (32), NBA (33), Dead Island 2 (35), Starfield (37), The Crew (38), Avatar (48), MK1 (53), Just Dance (82), SF6 (98), all those would be lost on a top 30 but didn't sell poorly at all.

For the top 20 of 2023 on Switch for Circana (Americas) there is only 1 3rd party title.

PS attach ratio have been increasing each gen PS2 sold 50% more than PS1 and still had a bigger attach ratio, PS4 sold 30% more than PS3 and have a substancial increase in attach ratio to PS3. Yes the bigger the userbase the most likely lower attach ratio due to more casuals. Regarding X360 the data was here on the site for a long time https://www.vgchartz.com/charts/platform_totals/TieRatio.php dunno the level of imprecision (because of the increase in digital sales they stopped tracking sometime during past gen, but for PS360 era those numbers were considered credible) and as you can see X360 was bigger than PS3. For other Xbox platforms I won't bother going through reports as MS isn't very transparent and any source would be indirect or trying to sum from leaks and so if you want to think it suddenly stopped being of the 10-12 range ok. But if you look the link you'll see that generally Nintendo attach ratio is lower than the other 3 and if you look for the portables they are much much lower than the consoles.

Switch 2 most likely won't have issue selling SW in Japan, if it is a successful system with similar portable focus it will keep a strong position in Japan. 

If you look at page 13 of their report (https://www.nintendo.co.jp/ir/pdf/2023/230509_3e.pdf) you'll see that for digital sales they count digital only titles -"Sales of downloadable versions of packaged software, download-only software, add-on content and Nintendo Switch Online, etc"

I would think Switch will close its lifetime near 10 attach ratio.

Bro you are  literally argueing that the PS5 makes up the gap with PS4 like the PS4 doesn't also have games charting below the top 30. On top of that, the top 30 has a low bar to reach and PS5 is struggling to keep more than 1. Obviously those games below the top 30 in a single region hardly makes up such a large gap on top of the PS4 also having software below the top 30. I would even argue the PS4 had more competition from 3DS, Vita, and WiiU than PS5 has against just Switch. More Nintendo games charting during 3DS/WiiU era along with Vita games than now but that would be interesting to comparison. 

Switch 3rd party sales could be considered mediocre but then again, so is its 3rd party support. So is that on the userbase or the 3rd parties lack of support? PS5 on the other hand has the support and sales the games at horrific level. Such as below WiiU and Vita. Mediocre is my description of the platform as a whole in Japan with good hardware sales (possibly due to exporting) and terrible software sales (possibly also due to exporting). Your fascination with Switch is irrelevant to the what we are discussing in a Japan sales thread. Switch will be the most successful platform in Japanese history, you trying to direct our attention to Switch's 3rd party global software sales and attach ratio is called deflection.

Your point on attach ratio going up with each passing gen for PS is interesting, I genuiely did not notice that. Thats a good call out. That doesn't prove it continued for Xbox though, the brand has sank massive since then. It will have an advantage over Switch for having a far smaller userbase but still receiving major 3rd party support but I highly doubt PS hasn't taken a good share of its software sales from Xbox. I do think Switch is competitive with those Xbox consoles attach ratio wise because PS since Xbox 360 has been dominate over the Xbox brand.

As for your Switch link, that is income. So Nintendo seems to include for digital only games but everything involving unit sales seems to lack digital only games. such as this I found on page 9, (chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.nintendo.co.jp/ir/pdf/2023/231107e.pdf), the notation says does not included download only software. This makes since because every blurb I see that does include digital only software also mentions including Nintendo Switch online, so clearly they are talking income. When talking software sales, Nintendo seems to include digital only software with income but does not include digital only software when talking units. I seriously think its because the unit sales would be far higher than the income they generate, so basically cheap mobile games like we see on Android and iOS. But those games would raise the attach ratio.