Im trying to say that third party success on nintendo machines is always mediocre compared to succes of third party games on other consoles. Its really hard to be even as half as succesfull as nintendo is on their own platforms.
You need to do your research. There are quite a few 3rd party games that sold more on Switch than anywhere else. Late release dates from being a new console have more to do with lower software sales than anything else.
And even if it does sell more on say PS4 or X1, the sales are still there for the developers to see profit. And that is why more and more 3rd party releases are starting to come day and date with the other versions now. Look at Wolfenstein New Blood, Mortal Kombat XI, DOOM Eternal, Crash Team Racing, Valkeria Chronicles 4, and Starlink as examples just off the top of my head.