Those other "obstacles" can also exist with a Pro Controller so it's not like they somehow are exclusive to joycons. You can bring your own joycons if your friend doesn't have enough. Every Switch comes with 2. Some people find the Pro Controller too big for example.
Now, on the second point it's all dependent on the game and you cannot say the use of motion controls on Splatoon, or ARMS is the same as in Just Dance, or Labo. The latter are specifically designed with the abilities and shape of the Joycon in mind, which the Pro Controller cannot offer and the same can be said about Mario Party.
Perhaps you'll be fine with it, but to most people it'd be awkward and alien to replicate said gestures with a two handled game controller. To remove the motion control mini games would also be narrowing game design, and in no way is it limiting accessibility since they're using the controller the system comes with out of the box. Two of which in fact.
And finally, all this argument is ignoring the major fact that the Pro Controller, much like its predecessor the Classic Controller was always positioned as a secondary control method and no developer is forced to use it in their software if they don't want to or doesn't fit their game.