Nintendo Switch is a console known for the seemingly endless ways you can use it, mainly stemming from its 3 main play modes (TV, Handheld, Tabletop). Any normal typical platform holder would've just made a straight hybrid and demand all games be played in both modes. But because of the Switch's unique design, Nintendo gives the developers near total creative freedom in how games can be presented on the console, which leads to things like modes, control schemes, even entire games that require the Switch and/or Joy-Con controllers to be used in specific way.

There's been some mixed feelings on this. Some say things like motion control games on Switch defeat the point of the system (even though you can just use tabletop mode, but whatever), and vice versa with touched. However I'd personally argue that this is a good thing for several reasons.

For one, it shows Nintendo isn't willing to force arbitrary policies down developers throats, which gives them more flexibility in how they can design Switch games. It also makes the Switch feel more original than simply a generic "hybrid". But perhaps importantly, It encourages people to try using the console in different ways. Last year, Nintendo's statistics showed that the vast majority of Switch owners use the system exactly as intended. IE, play both docked and un-docked. I'd argue a large part of this is because Nintendo has promoted and pushed players to use the system unconventionally. Sure, for the most part, you can use the Switch however you want. But if a game or mode in a game has some unorthodox set-up, and you simply try it, you might happen to like it, and would probably want to use it this way more often (or not).

So I don't see anything wrong with Nintendo not enforcing 100% compatibility with all play modes of the Switch, especially since it allows for more innovative games on the platform, and it's not like "handheld only" or "TV and Tabletop" only games are the majority on the system either, since the majority of Switch games can be easily adapted to all play-styles.

I hate that Super Mario Party doesn't support handheld mode. It is such a missed opportunity actually.

It's a game that was designed around Joy-Con motion controls and Multiplayer. I'd say it's understandable. 

Lucky for you it won't be the only Mario Party on the system, since 2015 a Mario Party game has released every year, 2012 if you exclude the one year gap in 2014. The Mario Party series gets new entry's like clockwork. 

i hate that Pokemon Lets GO cant be played with dual Joycons. mainly because in handheld mode there is an option to play with the controllers connected and using motion controls. and i just want to be able to do that while in TV mode

This is one instance where I have to kind of agree with the detractors. Considering handheld mode already has button based controls for catching, it makes no sense as to why they didn't just copy-paste those controls onto the Pro Controller or Joy-Con grip. My guess is that this is a more casual Pokemon game, and thus the target audience would be more familiar with using a Joy-Con.