> We should be vaccinating kids against all of them rather than sending them to Chickenpox parties.
This has been the standard of care ever since the vaccine became available in the 90s (US). The origin of the "parties" was that first-time chickenpox was perceived to be less harmful in children than adults prior to the vaccine, so you wanted to make sure people's first exposure wasn't in adulthood.
Is getting chickenpox the first as an adult more dangerous than as a kid not true or unproven?
Unfortunately that is not the case for me in the Netherlands. No Chickenpox vaccination is offered and making sure kids get it early is still considered the right way to do immunization.
The idea being that it's better for people to get it as kids, because if you give them vaccines as kids you'll have to give them boosters as adults. Whereas a latent disease will provide a lifetime of immunity.