The margin for error gets smaller every time the plates get thinner. The joining links have essentially eliminated user error from the equation, which is a good thing. I can't speak for Shimano as I haven't used one of their chains in decades, but certainly KMC and Wippermann joining links are easily worth their price for making the job simpler and quicker, even for a user with the skills and tools to create a riveted joint as good as a factory one.
The margin for error gets smaller every time the plates get thinner. The joining links have essentially eliminated user error from the equation, which is a good thing. I can't speak for Shimano as I haven't used one of their chains in decades, but certainly KMC and Wippermann joining links are easily worth their price for making the job simpler and quicker, even for a user with the skills and tools to create a riveted joint as good as a factory one.